Sustainable_Concrete_Pavement_508

Sustainable Concrete Pavements:
A Manual of Practice
January 2012
TECHNICAL EDITORS
Dr. Peter Taylor, Associate Director
National Concrete Pavement Technology Center, Iowa State University
Dr. Tom Van Dam, Principal Engineer, CTLGroup
(previously, Program Director, Materials and Sustainability Group, Applied Pavement Technology)
CO-AUTHORS
Dr. Tom Van Dam, Principal Engineer, CTLGroup
(previously, Program Director, Materials and Sustainability Group, Applied Pavement Technology)
Dr. Peter Taylor, Associate Director
National Concrete Pavement Technology Center, Iowa State University
Mr. Gary Fick, Vice President
Trinity Construction Management Services, Inc.
Dr. David Gress, Assistant Director
Recycled Materials Resource Center, University of New Hampshire
Ms. Martha VanGeem, Principal Engineer, CTLGroup
Ms. Emily Lorenz, Engineer, CTLGroup
EDITOR
Ms. Marcia Brink, National Concrete Pavement Technology Center, Iowa State University
DESIGNER
Ms. Mina Shin, Consulting Graphic Designer
Funded by the Federal Highway Administration (DTFH61-06-H-00011 (Work Plan 23))

©Institute for Transportation, Iowa State University Research Park, 2711 South Loop Drive, Suite 4700, Ames, IA
50010-8664
Printed in the United States of America January 2012
Sustainable Concrete Pavements: A Manual of Practice
ISBN: 978-0-9820144-2-4
This document fills a priority communications need identified in the Sustainability Track (Track 12) of the Long-
Term Plan for Concrete Pavement Research and Technology, a national research plan jointly developed by the
concrete pavement stakeholder community (www.cproadmap.org/ index.cfm).
FOR MORE INFORMATION
Tom Cackler, Director
Sabrina Shields-Cook, Managing Editor
National Concrete Pavement Technology Center
Iowa State University Research Park
2711 S. Loop Drive, Suite 4700
Ames, IA 50010-8664
515-294-7124
shieldsc@iastate.edu
www.cptechcenter.org/
MISSION
The mission of the National Concrete Pavement Technology
Center is to unite key transportation stakeholders
around the central goal of advancing concrete
pavement technology through research, tech transfer,
and technology implementation.
PHOTO CREDITS
Unless otherwise indicated in the text, all photographs
and illustrations used in this guide were provided by
the technical editor and co-author Dr. Peter Taylor.
DISCLAIMERS
The contents of this report reflect the views of the authors, who are responsible for the facts and the accuracy of the information presented
herein. The opinions, findings, and conclusions expressed in this publication are those of the authors and not necessarily those of the sponsors.
The sponsors assume no liability for the contents or use of the information contained in this document. This report does not constitute
a standard, specification, or regulation. The sponsors do not endorse products or manufacturers. Trademarks or manufacturers’ names
appear in this report only because they are considered essential to the objective of the document.
Iowa State University does not discriminate on the basis of race, color, age, religion, national origin, sexual orientation, gender identity, sex,
marital status, disability, genetic testing, or status as a U.S. veteran. Inquiries can be directed to the Director of Equal Opportunity and Diversity,
Iowa State University, 3680 Beardshear Hall, 515-294-7612.

CONTENTS
LIST OF FIGURES .................................... vii
LIST OF TABLES.......................................viii
ACKNOWLEDGMENTS............................ ix
PREFACE.................................................. x
Ch. 1. INTRODUCTION............................. 1
1. What is Sustainability?...........................................2
2. Concrete Pavements and Sustainability ..............2
3. Why Should the Concrete Pavement Industry
Care about Sustainability? ...................................3
4. Organization of This Manual .................................4
5. References.............................................................6
Ch. 2. PAVEMENT SUSTAINABILITY
CONCEPTS .......................................... 7
1. A Systems Approach
– Seeing the Big Picture ........................................8
2. Concrete Pavements...........................................10
Design Phase........................................................ 11
Materials .............................................................. 11
Construction......................................................... 12
Operations............................................................ 12
Preservation and Rehabilitation .......................... 12
Reconstruction and Recycling ............................ 13
3. Importance of Innovation...................................13
4. References...........................................................14
Ch. 3. DESIGNING SUSTAINABLE
CONCRETE PAVEMENTS ........................ 15
1. Context-Sensitive Design.....................................16
2. Concrete Pavement Design: The State of the
Practice................................................................17
3. Design Attributes Directly Enhancing
Sustainability .......................................................18
4. Alternative and Emerging Design
Technologies ......................................................18
Two-Lift Concrete Pavement ................................ 19
Precast Concrete Pavement Systems.................. 20
Roller-Compacted Concrete Pavement ............. 21
Interlocking Concrete Pavers............................... 22
Thin Concrete Pavement Design......................... 22
Pervious Concrete ................................................ 23
5. References...........................................................23
Ch. 4. SUSTAINABLE CONCRETE
PAVEMENT MATERIALS .......................... 25
1. Cementitious Materials.......................................26
More Efficient Clinker Production......................... 27
Reducing Portland Cement Clinker in Cement . 27
Reducing Cementitious Contents in Concrete .. 28
Reduce Concrete Used Over the Life Cycle ....... 28
2. Supplementary Cementitious Materials.............29
3. Emerging Cementitious Systems ........................30
4. Aggregates..........................................................30
Gradation ............................................................. 31
Aggregate Type.................................................... 31
Natural .................................................................. 31
Durability ............................................................... 32
5. Water....................................................................33
6. Admixtures...........................................................34
7. Reinforcement .....................................................34
8. Proportioning.......................................................35
9. References...........................................................35
Ch. 5. CONSTRUCTION.......................... 37
1. Overview of Construction Issues Related to
Sustainability .......................................................38
2. Traditional Slipform Paving Processes and
Impacts on Sustainability....................................38
Establishing and Operating a Plant Site ............. 38
Stockpiling Aggregate ......................................... 39
Establishing and Maintaining Haul Routes......... 40
Concrete Production............................................ 40
Transporting Concrete ......................................... 42
Concrete Placement and Finishing .................... 43
Surface Texturing .................................................. 44
Curing Concrete .................................................. 44
Sawing and Sealing Joints .................................. 45
3. New Developments in Concrete Pavement That
Could Improve Sustainability..............................45
Two Lift Concrete Pavements............................... 45
Roller-Compacted Concrete ............................... 46
4. References...........................................................46
Sustainable Concrete Pavements A Manual of Practice
v

CONTENTS, continued
Ch. 6. IMPACT OF THE USE PHASE.......... 47
1. Vehicle Fuel Consumption..................................48
2. Other Environmental Impacts During Use .........49
Solar Reflectance ................................................. 49
Lighting ................................................................. 50
Carbonation......................................................... 51
Run-Off and Leachate.......................................... 51
Traffic Delays ......................................................... 51
3. Summary..............................................................52
4. References...........................................................52
Ch. 7. CONCRETE PAVEMENT RENEWAL 55
1. Pavement Renewal Concepts ............................56
2. Pavement Evaluation Overview..........................57
3. Preventive Maintenance Treatments ..................58
Partial-Depth Repair ............................................. 58
Full-Depth Repair .................................................. 59
Load Transfer Restoration ..................................... 60
Diamond Grinding ............................................... 61
Summary............................................................... 62
4. Rehabilitation ......................................................62
Bonded Concrete Overlays ................................. 62
Unbonded Concrete Overlays ............................ 64
5. Summary..............................................................65
6. References...........................................................66
Ch. 8. END OF LIFE RECYCLING
CONCEPTS AND STRATEGIES ................ 67
1. Introduction to Recycled Concrete ...................68
2. RCA Properties ....................................................68
Physical Properties................................................ 69
Chemical Properties ............................................ 69
Mechanical Properties ........................................ 70
3. RCA used in Concrete.........................................70
Properties of Plastic RCA Concrete ..................... 70
Properties of Hardened RCA Concrete .............. 70
4. RCA in Foundations.............................................72
RCA as Unbound Base Material .......................... 72
RCA as Drainable Base ....................................... 73
RCA as Stabilized Base......................................... 73
5. Recycled Concrete in Other Applications ........74
6. References...........................................................74
Ch. 9. CONCRETE PAVEMENTS IN THE
URBAN ENVIRONMENT.......................... 77
1. The Urban Environment.......................................78
2. Reducing Environmental Impacts in the Urban
Environment.........................................................78
Light, Reflective Surfaces ...................................... 78
Reduced Emissions, Enhanced Fuel Efficiency... 79
Reduced Waste ................................................... 80
Reduced Storm Water Run-off ............................. 80
3. Reducing Societal Impacts in the Urban
Environment.........................................................81
Enhanced Aesthetics ........................................... 81
Noise Mitigation ................................................... 82
Health and Safety................................................. 82
Reduced User Delays ........................................... 82
4. Summary..............................................................83
5. References...........................................................83
Ch. 10. ASSESSMENT OF PAVEMENT
SUSTAINABILITY..................................... 85
1. Why Assessments are Important.........................86
2. Economic and Environmental Analyses ............86
Economic Analysis ............................................... 86
Environmental Assessment .................................. 87
3. Rating Systems ....................................................91
GreenLITES ............................................................ 91
Greenroads.....................................................93
4. Summary..............................................................95
5. References and Resources .................................96
Ch. 11. CONCLUSIONS AND FUTURE DE­
VELOPMENTS......................................... 97
1. Review..................................................................98
Pavement Sustainability Concepts ..................... 98
Designing Sustainable Concrete Pavements ..... 98
Selecting Materials............................................... 98
Construction......................................................... 99
The Use Phase ...................................................... 99
Pavement Renewal ............................................ 100
End of Life ........................................................... 100
Urban Environment ............................................ 100
Assessment ........................................................ 101
2. Innovation..........................................................101
vi
Sustainable Concrete Pavements A Manual of Practice

LIST OF FIGURES
Figure 2.1 Illustration of the current industrial
system....................................................................... 8
Figure 2.2 Illustration of the regenerative circular
economy .................................................................. 9
Figure 2.3 The concrete pavement life cycle............. 9
Figure 2.4 Features of concrete pavements that can
enhance sustainability .......................................... 11
Figure 3.1 RoboTex scans of 100×200 mm samples
showing variability of transverse tined surface
and its effect on noise level................................... 16
Figure 3.2 Two-lift pavement being constructed
in Kansas ................................................................ 19
Figure 3.3 Precast pavement being installed .......... 20
Figure 3.4 RCC pavement being placed ................ 21
Figure 3.5 Permeable interlocking concrete paver
blocks make an aesthetically pleasing, well-
drained pavement for low-volume streets and
parking lots............................................................. 22
Figure 3.6 Vehicular interlocking concrete pavers
being placed in a historic downtown area (note
the use of colored concrete to provide a visual
offset for the crosswalk) ......................................... 22
Figure 3.7 Pervious concrete being placed ............ 23
Figure 4.1 A cement kiln............................................ 26
Figure 4.2 CO 2 generation in cement
manufacturing ....................................................... 26
Figure 4.3 Scanning electron micrograph of C-S-H
and CaOH crystals................................................. 27
Figure 4.4 Backscatter electron image of fly ash
particles.................................................................. 29
Figure 4.5 Petrographic optical micrograph of slag
cement particles.................................................... 30
Figure 4.6 Reduction of cementitious content with
increasing coarse aggregate size ........................ 31
Figure 4.7 Rounded (left) and crushed natural
aggregates............................................................. 31
Figure 4.8 Light-weight fine aggregate .................... 32
Figure 4.9 Air-entrained concrete ............................. 34
Figure 4.10 Reinforcing for CRCP.............................. 35
Figure 5.1 Initial construction quality helps realize the
designed long-term performance ....................... 37
Figure 5.2 Front-end loader used for stockpiling
aggregate .............................................................. 40
Figure 5.3 Stockpiling aggregate with a radial
stacker .................................................................... 40
Figure 5.4 Central mix concrete plant ..................... 41
Figure 5.5 Ready mix concrete plant ....................... 41
Figure 5.6 Transit mix concrete truck ........................ 42
Figure 5.7 Tractor trailer concrete hauling unit ........ 42
Figure 5.8 Washout pit used to clean concrete
trucks ...................................................................... 42
Figure 5.9 Longitudinal tining ................................... 44
Figure 5.10 Artificial turf drag texture........................ 44
Figure 5.11 Diamond-ground texture ....................... 44
Figure 5.12 Top lift being placed on the bottom lift
................................................................................ 46
Figure 5.13 Two-lift paving on I-70 in Kansas ............ 46
Figure 5.14 RCC placement ..................................... 46
Figure 6.1 Ecoprofile of different life-cycle phases
from a typical road ................................................ 48
Figure 6.2 Heat islands for various areas of
development.......................................................... 50
Figure 6.3 Effect of pavement type and albedo on
pavement surface temperature............................ 50
Figure 6.4 Depth of carbonation determined by the
phenolphthalein test (pink two-thirds of the sam­
ple is not carbonated) .......................................... 51
Figure 6.5 Traffic delays caused by construction .... 52
Figure 7.1 Typical pavement performance
curve showing ideal times for the application of
pavement preservation, rehabilitation, and recon­
struction.................................................................. 56
Figure 7.2 Comparison of treatment costs at
different pavement condition ratings (PCRs)....... 56
Figure 7.3 Illustration of typical impacts of
preventive maintenance and rehabilitation on
concrete pavement condition.............................. 57
Figure 7.4 Damaged material has been milled out
in a partial-depth repair ........................................ 59
Figure 7.5 Illustration of distress extent, with distress
at the bottom of the slab extending beyond that
observed at the surface ........................................ 59
Figure 7.6 Schematic illustration of load transfer
restoration............................................................... 60
Figure 7.7 Dowel bars on chairs with end caps and
compressible inserts in place ready to be inserted
into prepared slots ................................................. 60
Sustainable Concrete Pavements A Manual of Practice
vii

LIST OF FIGURES, continued
Figure 7.8 Diamond ground surface after years of
service .................................................................... 61
Figure 7.9 Typical applications for bonded and
unbonded concrete overlays on existing concrete
and asphalt/composite pavements .................... 63
Figure 7.10 Bonded overlay ...................................... 64
Figure 7.11 Unbonded overlay ................................. 65
Figure 8.1 Recycled concrete aggregate (RCA) .... 68
Figure 9.1 Photocatalytically active colored
concrete pavers in Japan..................................... 79
Figure 9.2 Pervious concrete..................................... 80
Figure 9.3 Water passing through pervious
concrete ................................................................. 80
Figure 9.4 Blome Granitoid concrete pavement
constructed in 1906 in Calumet, Michigan; the
brick pattern was stamped into the surface to
keep horses from slipping ..................................... 81
Figure 9.5 Modern Blome Granitoid concrete
pavement............................................................... 81
Figure 9.6 A potentially quiet surface (viewed from
the side) ................................................................. 82
Figure 10.1 An LCI accounts for all materials and
energy needed to make and use a product, and
the emissions to air, land, and water associated
with making and using that product ................... 88
Figure 10.2 Three alternatives used in a limited LCA
to determine environmental impact of design
and material choices ............................................ 90
Figure 10.3 Results of the LCA of the three Kansas
two-lift alternatives.................................................. 91
LIST OF TABLES
Table 5.1 Summary of Concrete Pavement
Construction Practices That Enhance Pavement
Sustainability ..........................................................39
Table 5.2 Concrete Pavement Surface Texture
Types.......................................................................44
Table 7.1 Pre-Overlay Repair Recommendations for
Bonded Concrete Overlays...................................63
Table 7.2 Recommended Transverse Joint Spacing
for Unbonded Concrete Overlay ..........................65
Table 7.3 Pre-Overlay Repair Recommendations for
Unbonded Concrete Overlays ..............................65
Table 10.1 Relevant Mixture Design Features in the
Kansas Two-lift LCA Evaluation...............................90
Table 10.2 GreenLITES Certification Levels ...............91
Table 10.3 Greenroads Certification Levels .............93
viii
Sustainable Concrete Pavements A Manual of Practice

ACKNOWLEDGMENTS
The co-authors and the National Concrete Pavement
Technology Center are grateful to the many knowledgeable
and experienced professionals, public and
private, who contributed to the development of this
guide. First and foremost, we are indebted to the Federal
Highway Administration (FHWA) for its generous
support and sponsorship (DTFH61-06-H-00011,
Work Plan 23). The agency recognized a critical information
need within the national concrete pavement
community and made the commitment to fill it.
The content of this guide reflects the expertise and
contributions of the technical advisory committee,
whose members represent the wide variety of discrete
processes and variables, including regional issues, that
must be considered to effectively optimize the sustainability
of concrete pavements. While the authors
generated the overall content, it was the technical advisory
committee’s careful reviews of drafts, thoughtful
discussions, and suggestions for revisions and refinements
that make this guide a straightforward, comprehensive
resource for practitioners. We appreciate the
invaluable assistance of the committee members:
Mr. Fares Abdo, former Program Manager for Water
Resources, Portland Cement Association
Ms. Gina Ahlstrom, Pavement Engineer,
Federal Highway Administration
Ms. Janet Attarian, Project Director, Department of
Transportation Streetscape and Sustainable Design
Program, City of Chicago
Mr. Barry Descheneaux, Holcim
Mr. James Duit, President, Duit Construction
Ms. Kelsey Edwardsen, Structural Engineer, Bechtel
Ms. Dulce Rufino Feldman, Transportation Engineer,
California Department of Transportation
Dr. Anthony Fiorato, Executive Director,
Slag Cement Association
Mr. Dale Harrington, Principal Senior Engineer, Snyder
and Associates, Inc.
Mr. Brian Killingsworth, Senior Director of Pavement
Structures, National Ready Mixed Concrete Association
Mr. Steve Kosmatka, Vice President of Research and
Technical Services, Portland Cement Association
Mr. Lionel Lemay, Senior Vice President of Sustainable
Development, National Ready Mixed Concrete
Association
Mr. Kevin McMullen, Director,
Wisconsin Concrete Pavement Association
Mr. Joep Meijer, President, The Right Environment
Dr. Steve Muench, Associate Professor of
Environmental and Civil Engineering, University of
Washington
Mr. Andrew Pinneke, LEED and Sustainable
Construction Coordinator, Lafarge North America
Mr. Tim Smith, past Director, Transportation and
Public Works, Cement Association of Canada
Dr. Mark Snyder, Vice President, Pennsylvania
Chapter, American Concrete Pavement Association
Dr. Michael Sprinkel, Associate Director, Virginia
Transportation Research Council
Dr. Larry Sutter, Director, Michigan Tech
Transportation Institute, Michigan Technological
University
Mr. Sam Tyson, Task Manager, Concrete Pavement
Technology Program, Federal Highway Administration
Mr. Leif Wathne, Vice President, American Concrete
Pavement Association
Sustainable Concrete Pavements A Manual of Practice
ix

PREFACE
Sustainable Concrete Pavements: A Manual of Practice is
a product of the National Concrete Pavement Technology
Center at Iowa State University’s Institute for
Transportation, with funding from the Federal Highway
Administration (DTFH61-06-H-00011, Work
Plan 23). Developed as a more detailed follow-up to a
2009 briefing document, Building Sustainable Pavement
with Concrete, this guide provides a clear, concise, and
cohesive discussion of pavement sustainability concepts
and of recommended practices for maximizing
the sustainability of concrete pavements.
The intended audience includes decision makers
and practitioners in both owner-agencies and supply,
manufacturing, consulting, and contractor businesses.
Readers will find individual chapters with the most
recent technical information and best practices related
to concrete pavement design, materials, construction,
use/operations, renewal, and recycling. In addition,
they will find chapters addressing issues specific to
pavement sustainability in the urban environment and
to the evaluation of pavement sustainability.
Development of this guide satisfies a critical need
identified in the Sustainability Track (Track 12) of the
Long-Term Plan for Concrete Pavement Research and
Technology (CP Road Map). The CP Road Map is a
national research plan jointly developed by the concrete
pavement stakeholder community, including Federal
Highway Administration, academic institutions,
state departments of transportation, and concrete pavement–related
industries. It outlines 12 tracks of priority
research needs related to concrete pavements. CP
Road Map publications and other operations support
services are provided by the National Concrete Pavement
Technology Center at Iowa State University. For
details about the CP Road Map, see www.cproadmap.
org/index.cfm.
x
Sustainable Concrete Pavements A Manual of Practice

Chapter 1
INTRODUCTION
Tom Van Dam
Peter Taylor
It is becoming increasingly apparent that a host of
human activities and development practices are
negatively affecting the economic, environmental, and
social well-being of the planet, putting future generations
of humanity, as well as of other species, at risk.
Confronted with this reality, stakeholders in the pavement
industry are being challenged to adopt practices
that maintain economic vitality while balancing environmental
and societal needs.
At the same time, stakeholders are facing other challenges:
Pavements are aging and deteriorating; onethird
of the road system, about 1.3 million miles, is in
poor condition or worse, receiving a grade of D- in the
American Society of Civil Engineers report card (ASCE
2009A). Traffic volumes and vehicle loads continue
to increase, putting more demands on the already
stressed pavement system and, in major metropolitan
areas, resulting in serious congestion problems. Roadway
agency budgets continue to fall short of needed
funds, with an estimated $115.7 billion annual shortfall
from funding required to substantially improve
pavement conditions. These challenges exist not only
in a time of economic uncertainty but also within the
developing realization that the environmental and
social impacts of these pavements systems are great.
The people responsible for the management, design,
construction, maintenance, and rehabilitation of the
deteriorating network of pavements are overwhelmed,
recognizing that the current approach to solving problems
inherent in the nation’s pavement infrastructure is
not sustainable. What is needed is a new approach, the
implementation of truly sustainable pavement solutions
that result in reduced economic cost over the life
cycle, lessened environmental impact, and enhanced
societal benefit, while maintaining the system in a high
level of service for perpetuity. Recognizing this, many
public agencies are adopting more “sustainable” practices
and are beginning to rate, incentivize, and even
award projects based on their demonstrated ability to
enhance sustainability.
Yet, the basic questions remain: What is sustainability?
What attributes of concrete pavements can make them
a sustainable choice? Why is an emphasis on sustainability
important for the concrete pavement industry?

1. What is Sustainability?
A basic definition of sustainability is the capacity to
maintain a process or state of being into perpetuity,
without exhausting the resources upon which it
depends nor degrading the environment in which it
operates. In the context of human activity, sustainability
has been described as activity or development “that
meets the needs of the present without compromising
the ability of future generations to meet their own
needs” (WCED 1987).
Typically, three general categories (or pillars) of sustainability
are recognized: economic, environmental,
and social. When activities are sustainable, no pillar is
ignored; instead, a workable balance among the three
often-competing interests must be found. Together, the
three pillars form what is commonly called the “triple
bottom line” (Elkington 1994). This concept can be
expressed graphically as shown in Figure 1.1, which
illustrates that sustainable solutions are those that
incorporate all elements of the triple bottom line.
Although this is a common definition of sustainability,
it is somewhat dissatisfying as it doesn’t define what
is and is not important and it doesn’t provide clear
Social
Progress
Socio-
Environmental
Socio-
Economic
Economic
Growth
Sustainability
Eco-
Efficiency
Environmental
Stewardship
Figure 1.1 Graphical representation of sustainability’s
“triple-bottom line” of economic, environmental,
and societal considerations
direction as to what must be done differently in the
future to improve upon the present. This manual
provides such definitions and directions, as they are
currently understood, regarding concrete pavements.
Balancing economic, environmental, and societal
factors for a pavement project requires identifying
applicable factors in each category, collecting data for
the factors to be evaluated, applying tools to quantify
the impact of each factor, and assessing the combined
impact of the factors in relationship to one another.
Complicating the process is the fact that factors must
be identified and measured/estimated during all stages
of a pavement’s life—design, materials selection, construction,
operation, preservation/rehabilitation, and
reconstruction/recycling. In other words, assessment
of the sustainability of a project will require the use of
a robust, sophisticated analysis.
It is recognized that a complete assessment of sustainability
is beyond the current state of the practice
and, in truth, may be impossible. Still, the application
of available tools will assist in making incremental
progress in achieving more sustainable concrete
pavements.
2. Concrete Pavements and
Sustainability
Concrete pavements suffer from a perception that they
contribute a considerable amount of carbon dioxide
(CO 2 ) to the atmosphere due to the use of portland
cement that binds the aggregates together. Although
portland cement manufacturing is an energy intensive
process and does result in significant CO 2 emissions,
partly due to the pyroprocessing required and partly
due to the calcination of limestone (discussed in
Chapter 4), advances in cement production have
greatly decreased these impacts relative to even a few
years ago. In addition, and just as important, modern
concrete for pavements uses less portland cement per
cubic yard relative to past practices, and thus concrete
pavements have a lower carbon footprint than at any
time in history. Further, future innovations will ensure
additional improvements in reducing the carbon
footprint and energy use over the next decade. When
all aspects of sustainability are considered, especially
when accounting for the pavement’s life cycle,
2
Ch. 1. INTRODUCTION
Sustainable Concrete Pavements A Manual of Practice

properly designed and constructed concrete pavements
are clearly part of a sustainable transportation system.
Following are a few general attributes of concrete
pavements that can make them a sustainable choice:
• Long life: Achieving the desired design life with
minimal future preservation activities results in
reduced user delays and associated economic and
environmental impacts over the life cycle.
• Smooth, quiet, and safe over the life cycle: Motorists
experience a comfortable ride; drag is minimized
for enhanced vehicle efficiency; pavement
surface visibility and skid resistance are maximized
through minimal preservation activities.
• Increased use of industrial residuals and reduced
use of non-renewable resources.
• Fully recyclable.
• Cost effective: Demonstrated over the life cycle,
concrete pavements preserve their equity long into
the future.
• Minimal impact to the surrounding environment:
In-place concrete pavements have no adverse effect
on, and are not adversely affected by, atmospheric
conditions, the natural environment, etc.
• Minimal traffic disruption during construction and
preservation activities.
• Community friendly: Aesthetically pleasing, appropriately
textured, light colored surfaces reduce
ambient noise, emissions, surface run-off, urban
heat, and artificial lighting needs, resulting in a
positive local and global impact.
Strategies for design, material selection, construction,
operation, maintenance/rehabilitation, and reconstruction/recycling
are already being implemented that
create concrete pavements with these attributes. Some
of these strategies have been part of standard practice
for over 100 years, resulting in incredible longevity
and cost effectiveness, the hallmarks of concrete pavement.
Others strategies, although demonstrated, are
in the initial phase of implementation. This manual of
practice focuses on concrete pavement strategies that
can be readily implemented to enhance sustainability.
3. Why Should the Concrete
Pavement Industry Care
about Sustainability?
Before considering strategies to increase sustainability, it
is first necessary to take a step back to consider why this
is important to the concrete pavement industry.
First, sustainability is not really new; it simply raises the
bar for good engineering. Good engineering has always
entailed working with limited resources to achieve an
objective. What has changed is the scope of the problem,
along with the period of time over which a project
is evaluated. Whereas in the past economic factors were
paramount, now environmental and social factors must
be considered equally with economic factors. Whereas
in the past initial costs and other initial impacts were
often paramount, now the span of time in the analysis
is increased to the entire life cycle of a project, and all
impacts (both positive and negative) are considered
from the point of inception (e.g., mining of raw materials)
to end of life (e.g., recycling). This type of analysis
is often referred to as a “cradle to cradle” analysis
(McDonough and Braungart 2002).
Such an all-encompassing scope over such a long analysis
period requires a systems approach to fully realize
the opportunities to implement sustainable design. At
this juncture, sustainable design is not about achieving
perfection but about balancing competing and
often contradictory interests to bring about incremental
change. Although most civil engineers find the idea of
sustainability as the new standard for good engineering
to be a challenging prospect, many find it engaging as
well. As sustainable design continues to evolve, so will
the role played by the concrete pavement industry.
Second, sustainability is increasingly being demanded
by a diverse number of stakeholders. One major group
of stakeholders is the public. ASCE’s Board of Direction
recently approved the following statement (ASCE 2009B):
The public’s growing awareness that it is possible
to achieve a sustainable built environment, while
addressing such challenges as natural and man-made
disasters, adaptation to climate change, and global
water supply, is reinforcing the civil engineer’s changing
role from designer/constructor to policy leader
and life-cycle planner, designer, constructor, operator,
and maintainer (sustainer).
Sustainable Concrete Pavements A Manual of Practice Ch. 1. INTRODUCTION 3

This statement recognizes that one of the driving
forces for the changing role of the civil engineer as a
“sustainer” is the “public’s growing awareness” that a
more sustainable built environment is achievable. Civil
engineers are being required to examine alternative
solutions that a few years ago might not have been
considered. This idea is clearly annunciated in the
integrated global aspirational vision statement adopted
at The Summit on the Future of Civil Engineering held in
2006, which stated that civil engineers are “entrusted
by society to create a sustainable world and enhance
the global quality of life” (ASCE 2007). This is a large
aspiration, reflecting the responsibility entrusted by
the public to those charged with designing, constructing,
operating, preserving, rehabilitating, and recycling
infrastructure including concrete pavements.
Another group of stakeholders, more directly relevant
to the concrete pavement industry, includes
local, state, and federal pavement owner agencies. As
mentioned previously, various agencies have begun to
require that sustainability metrics be measured on paving
projects and may use such metrics in the selection
process for future transportation projects.
Third, today’s increasing focus on sustainable infrastructure
offers an opportunity for the concrete pavement
industry to communicate the positive contributions
inherent in concrete pavement. Because of its
versatility, economy, local availability, and longevity,
concrete is the most commonly used building material
on the planet; it is not hyperbole to say that modern
civilization is literally built on concrete. Due to the
sheer volume of concrete in use and its many sustainable
attributes, it has a relatively large environmental
footprint as well as immense positive impacts on
sustainability. The concepts related to sustainability
provide a positive language through which industry
can communicate the good being done through the
use of concrete pavement rather than solely disputing
unjustifiable perceptions of harm.
Fourth, adopting sustainability principles and practices
will make the concrete pavement industry more attractive
to a younger workforce. Peter Senge et al. (2009),
in their book, The Necessary Revolution: How Individuals
and Organizations are Working Together to Create a
Sustainable World, state that employees are making
career choices based on an organization’s commitment
to sustainability. Yet even ASCE, in the last sentence of
the Board of Direction’s statement cited earlier (ASCE
2009B), has recognized that civil engineers are often
perceived as part of the problem, not the solution:
“Civil engineers are not perceived to be significant contributors
to a sustainable world.” With this backdrop it
is clear that, to attract the young talent needed for the
future, industry must change such negative perceptions
through the advancement of sustainable concrete
infrastructure, including pavements.
And, finally, enhancing sustainability will make the
concrete pavement industry more innovative and more
competitive. This can be observed already through
such diverse innovations as in-place recycling of existing
concrete pavement, two-lift construction, safe and
quiet surface characteristics, pervious concrete, optimized
aggregate gradations that reduce cementitious
material content, and the trend toward concrete with
higher supplementary cementitious material (SCM),
to name a few. Each of these examples clearly demonstrates
positive economic, environmental, and social
impacts. Emerging concrete technologies that are
poised to bring even more dramatic positive changes
include photocatalytic cements to treat air pollution,
carbon sequestering cements and aggregates, further
increases in SCM content, embedded sensing technologies
for construction and infrastructure health
monitoring, and advanced construction processes that
minimize energy use and emissions.
The challenge to the industry is to step out of the box
and, instead of focusing on simply meeting existing
specifications, “re-imagine” what a concrete pavement
can be and work with the various stakeholders to further
increase the economic, environmental, and social
benefits inherent in concrete pavements.
4. Organization of This Manual
Fortunately, many best practices already exist for constructing
new concrete pavements as well as preserving
or rehabilitating existing ones in a manner that significantly
contributes to the sustainability of the nation’s
highway system. Decision makers, engineers, material
suppliers, and contractors need practical guidance on
adopting these solutions and considering their relative
benefits in the context of limited budgets, increased
4
Ch. 1. INTRODUCTION
Sustainable Concrete Pavements A Manual of Practice

performance requirements, and congested traffic situations.
This manual of practice is designed to help, as
summarized in the following brief description of its
chapters:
1. Introduction – This chapter generally defines
sustainability and its significance for the concrete
pavement industry.
2. Pavement Sustainability Concepts – This chapter
focuses on specific attributes of pavements, with a
particular emphasis on concrete pavements, that
impact sustainability. The life cycle, including cradle-to-gate
and ideal cradle-to-cradle closed loop
systems, is described. Technologies that extend
pavement life and/or reduce the use of energy
intensive and environmentally damaging materials
and practices will be emphasized. This chapter
presents a conceptual cradle to grave approach to
concrete pavement, introducing the specific topics
discussed in detail in Chapters 3 through 10.
3. Designing Sustainable Concrete Pavements – Sustainability
is not an accident, instead requiring
a thoughtful, systematic approach to concrete
pavement design. Sustainable solutions make
the best use of locally available materials without
compromising, and possibly even enhancing,
pavement performance. Design attributes that have
been shown to enhance sustainability, including
extended service life designs and two-lift construction,
are featured, but emerging concrete pavement
systems including precast concrete pavements and
thin concrete pavements are also introduced.
4. Sustainable Concrete Pavement Materials – Materials
used to make concrete for pavements have a
large impact on the sustainability of the pavement.
This chapter details the importance of making
durable concrete that withstands the environment
during its service life. It also emphasizes the
need to use the appropriate amount of cementing
materials, discussing the advantages of reducing
portland cement through good mixture design and
the use of supplementary cementitious materials,
including fly ash and slag cement. The emergence
of lower energy, lower emissions cements (including
portland-limestone cements, carbon neutral/
sequestering cements, and geopolymers) is also
discussed. The chapter concludes with a discussion
of concrete making materials, with specific emphasis
on the use of recycled and industrial byproduct
materials used as aggregate.
5. Construction – Various elements of construction
have an impact on the overall sustainability of a
concrete pavement. Obvious elements include the
energy consumed and waste generated during the
constructions process, including emissions and
solid waste. Water use during the entire construction
process is another important element, as is
the generation of noise and particulate matter,
especially as it relates to the social impact in urban
environments. This chapter discusses these construction-related
elements and presents strategies
to minimize the environmental aspects of concrete
paving project.
6. The Impact of the Use Phase – The versatility of
concrete as a paving material offers many sustainable
attributes that are not always obvious. Operational
considerations are an extremely important
consideration, as it is estimated that at least 85
percent of the environmental footprint of a pavement
is incurred after it is built during its service
life. The most prominent impact is from the
vehicles operating on the pavement, most notably
from the fuel consumed, which is influenced by
pavement roughness and possibly by the stiffness
of the surface layer. Recent research has focused on
the influence of radiative forcing, which is related
to surface reflectivity and may be contributing to
global climate change even from rural pavements
(impacts in the urban environment are addressed
separately in Chapter 9).
7. Concrete Pavement Renewal – Preservation and
rehabilitation play an important role in ensuring
concrete pavement longevity while maintaining the
highest level of serviceability. As such, they directly
contribute to the sustainability of the concrete
pavement. This chapter discusses various preservation
and rehabilitation strategies that can be
applied to increase concrete pavement sustainability,
directing the reader to appropriate sources for
further information. The main focus of this chapter
is on how timely and appropriate preservation and
rehabilitation can be used to enhance sustainability
Sustainable Concrete Pavements A Manual of Practice Ch. 1. INTRODUCTION 5

over the life cycle. The uses of diamond grinding
and concrete overlays are featured.
8. End of Life Recycling Concepts and Strategies –
This chapter discusses the recycling of existing
road materials into new pavement. The focus is on
recycling concrete, but recycling hot-mix asphalt
and unbound granular materials into a new concrete
pavement is also discussed. Specific guidance
on the appropriate use of recycled material as
aggregate in new concrete is provided, as is guidance
for its use in supporting layers. Emerging in
situ recycling techniques are discussed as a sustainable
alternative.
9. Concrete Pavements in the Urban Environment –
This chapter discusses the unique characteristics of
concrete pavement that make it ideal for use in an
urban environment. Of specific interest is its high
surface reflectivity index (SRI), which can help mitigate
the urban heat island effect and decrease the
cost of artificial lighting. The urban environment is
also a location where photocatalytic cements and
coatings can be used to provide additional reflectivity
while treating nitrogen oxide (NO x ), (SO x ),
and volatile organic compounds. Concrete can
also be colored and molded to create aesthetically
pleasing designs that not only are beautiful but
also can be used to calm traffic in urban neighborhoods,
making them more pedestrian friendly.
Alternatively, textured concrete surfaces can be
designed to be exceptionally quiet for high-speed
operations. Addressing surface run-off is another
critical need in urban settings, making the use of
pervious concrete an ideal choice for many paved
surfaces.
10. Assessment of Pavement Sustainability – It is
essential that the sustainability of pavements be
systematically and accurately assessed to recognize
improvement and guide innovation. This chapter
reviews current approaches to assessing pavement
sustainability, including the Greenroads TM rating
system. It also describes the rigorous environmental
life cycle assessment (LCA) approach as a path
to more fully quantify and optimize the environmental
factors contributing to the sustainability of
concrete pavements.
11. Conclusions and Future Developments – This chapter
briefly summarizes the information presented in
this manual. It also discusses emerging technologies
that are not yet ready for implementation but
have the potential to significantly impact concrete
pavement sustainability within the next decade. Its
goal is to inform the reader of developing trends as
well as foster innovation and encourage the adoption
of technologies that will lead to more sustainable
concrete pavements.
Due to the dynamic nature of the topic, this manual
is a “living document” that will be revised regularly
to reflect evolving understandings of issues related to
enhancing concrete pavement sustainability.
5. References
American Society of Civil Engineers (ASCE). 2007. The
Vision for Civil Engineering in 2025. Based on The Summit
on the Future of Civil Engineering—2025 held
June 21–22, 2006. Reston, VA: American Society of
Civil Engineers.
ASCE. 2009A. 2009 Report Card for America’s Infrastructure.
Reston, VA: American Society of Civil Engineers.
(www.infrastructurereportcard.org/sites/default/
files/RC2009_full_report.pdf, accessed Nov. 10, 2011)
ASCE. 2009B. “Board of Direction Views Sustainability
Strategy as Key Priority.” ASCE News 34:1.
Elkington, J. 1994. “Towards the Sustainable Corporation:
Win-Win-Win Business Strategies for Sustainable
Development.” California Management Review, 36:2.
McDonough, W., and M. Braungart. 2002. Cradle to
Cradle: Remaking the Way We Make Things. New York,
NY: North Point Press.
Schley. 2008. The Necessary Revolution: How Individuals
and Organizations Are Working Together to Create a
Sustainable World. New York, NY: Doubleday.
WCED (World Commission on the Environment and
Development, United Nations). 1987. Our Common
Future: The Report of the World Commission on Environment
and Development. New York, NY: Oxford University
Press.
6
Ch. 1. INTRODUCTION
Sustainable Concrete Pavements A Manual of Practice

Chapter 2
PAVEMENT SUSTAINABILITY
CONCEPTS
Tom Van Dam
This chapter focuses on the broad application of sustainability
concepts as applied to the natural world, to
pavement systems in general, and then specifically to
concrete pavements. It begins with a brief introduction
to a systems approach to understanding sustainability,
introducing the concept of the life cycle, including
cradle-to-grave and cradle-to-cradle closed loop
systems. The chapter then discusses the life cycle of
concrete pavement and how the adoption of sustainable
practices results in continued economic, environmental,
and social health. The chapter concludes with
a discussion of innovation, describing how innovation
is driven through the adoption of sustainability
principles.

1. A Systems Approach
– Seeing the Big Picture
This manual of practice is specifically written to
address the needs of transportation and pavement
professionals to facilitate the adoption of sustainable
concrete pavement practices. As such, the focus is very
specific and the scope is necessarily narrow. Yet it is
essential that concrete pavement professionals develop
an appreciation of the role they play in creating a more
sustainable world by understanding the relationships
that exist between the industrial system on which
the economy is built and the natural world, which
includes social and ecological health.
Until fairly recently, decision making was largely based
on consideration of the “bottom line,” which was
understood in purely economic terms. In The Necessary
Revolution, Senge et al. (2008) state that it is not
surprising that few people paid attention to degrading
social and environmental conditions under this
model of industrial activity as it “focuses on parts and
neglects the whole.” As a result, achieving immediate
tangible economic goals was rewarded while ignoring
long-term, larger system needs was largely without
consequence. This is evident upon examination of
production during the industrial age, in which narrow
thinking led to widespread dependency on non-regenerative
energy and material resources, inefficient and
waste-generating production, and economic growth
driven through the consumption of products and
services.
Figure 2.1 (Senge et al. 2008) illustrates this model
of production, showing how the current industrial
system (e.g., goods in production and use) is part of
a larger system that can broadly be considered as the
natural world. This natural world includes regenerative
resources (e.g., forest, croplands, and fisheries) and
non-regenerative resources (e.g., oil, minerals). Regenerative
resources are part of the ecological system, and
as long as such a resource is replenished more quickly
than it is consumed, the resource is sustained indefinitely.
On the other hand, non-regenerative resources
are extracted from the earth, and since they are not
regenerated within a useful timeframe, they may in
time become depleted. Significantly, the extraction and
harvesting of resources and the production and use of
goods generate waste. Depending on the nature of this
waste, it can compromise the ecological system and
its ability to produce regenerative resources that are
essential to the health of humanity as well as all life
on the planet. Not shown in Figure 2.1, but essential
to understanding sustainability, is how the current
industrial system impacts social systems (e.g., communities,
families, culture).While improving the quality of
life in some aspects, the system also results in anxiety,
inequality, and stresses on societies that in the extreme
are manifest as widespread poverty and war.
As an alternative, Senge et al. (2008) offer the concept
of a regenerative circular economy illustrated in
Figure 2.2. This economy reflects a movement towards
greater use of harvested regenerative resources and a
dramatic reduction in accumulating waste, resulting in
a more sustainable world in which resources are regenerated
and waste minimized or eliminated. In this
model, there is still a need for extractive industries,
but the greater dependency on renewable resources
ensures less system-wide impact due to extraction. It
also establishes a close link between economic growth
and natural resource regeneration, which requires
healthy ecological systems. Biodegradable waste from
SOLAR
ENERGY
PHOTOSYNTHESIS
Growth
Ecological
Systems
Regeneration
Harvesting
Natural Resources
Extracting
Non-
Regenerative
resources
Clean Air
Drinkable Water
Fertile Soil
Pollination
Stable Climate
Goods in
Production
Waste from
Extracting and
Manufacturing
Production
Accumulating Waste
CONSUMPTION
PRODUCTS SERVICES
Goods in
Use
Waste from
Use
Waste from
Discard
Figure 2.1 Illustration of the current industrial system
(Senge et al. 2008)
8
Ch. 2. PAVEMENT SUSTAINABILITY CONCEPTS
Sustainable Concrete Pavements A Manual of Practice

industrial processes are fed into the ecological system
to support resource development. Wastes not used to
support natural systems are used as raw materials for
other industrial processes, thus resulting in waste minimization
while at the same time reducing demands
to extract or harvest additional resources. Ideally, the
economic system will ultimately mimic that which
happens in nature, in which the concept of waste is
eliminated and all waste becomes food for another
process (McDonough and Braungart 2002).
Inherent in this concept is the understanding that
sustainability requires a life-cycle perspective, in which
the economic, environmental, and social benefits and
costs of any product or service are considered over its
entire life. This is partially illustrated in Figure 2.2,
which shows material extraction, manufacturing, and
goods in use, with a circular flow of natural and technical
materials back into regeneration and production.
What is lacking in this illustration is the temporal
nature of the life cycle, which in the case of a pavement
may be 40 or more years. Conventionally, we
think of pavement life as linear, moving from the
“cradle” (design, material extraction and processing,
SOLAR
ENERGY
PHOTOSYNTHESIS
Clean Air
Drinkable Water
Fertile Soil
Pollination
Stable Climate
Health vs. Stress
Security vs. Fear
Social Harmony vs. Mistrust
Peace vs. Unresolvable Conflicts
and construction) through its service life and finally
to the “grave” (pavement removal and reconstruction).
This cradle-to-grave concept is counter to sustainability.
Sustainability instead requires a “cradle-to-cradle”
approach in which the end of life is part of a new
beginning (McDonough and Braungart 2002). For
concrete pavements, this is simply illustrated in Figure
2.3, in which design, materials processing, construction,
operations, preservation and rehabilitation, and
reconstruction and recycling are joined in a continuous
loop.
Although conceptually this may seem overwhelming,
applying sustainability principles at a practical,
implementable level using today’s technologies simply
means finding opportunities to minimize environmental
impact while increasing economic and social
benefit. Already, the value of life-cycle cost analysis
(LCCA) is recognized as a way to consider current and
future anticipated economic impacts over the life of
the design. In addition, as is discussed in Chapter 10,
a number of approaches to assess sustainability are
emerging and will soon be available for implementation
by the concrete pavement industry, including the
use of life-cycle analyses that address environmental
impacts over the life of a pavement. Yet, only by stepping
away from the larger issues of the economy as a
whole and instead focusing on the project level can
these overarching sustainability concepts be implemented
into actionable and measurable activities that
will be used by the concrete pavement industry.
Growth
Ecological
Systems
Regeneration
Growth
Social
Systems
Regeneration
CONSUMPTION
Design
Harvesting
Natural Resources
Extracting
Non-
Regenerative
resources
Goods in
Production
Waste from
Extracting and
Manufacturing
Production
PRODUCTS SERVICES
Goods in
Use
Waste from
Use
Waste from
Discard
Materials
Processing
Construction
Reconstruction
and Recycling
Preservation and
Rehabilitation
Accumulating Waste
Operations
Figure 2.2 Illustration of the regenerative circular Figure 2.3 The concrete pavement life cycle (Van
economy (Senge et al. 2008) Dam and Taylor 2009).
Sustainable Concrete Pavements A Manual of Practice Ch. 2. PAVEMENT SUSTAINABILITY CONCEPTS 9

To do so, it is first necessary to recognize that a concrete
pavement can be considered as a project-level
system within the larger system previously discussed.
This project-level system has its own context, which
is sensitive to the needs defined by the various stakeholders
and the environmental setting in which the
project is to be constructed. The context establishes
the constraints under which project decisions are
made, from which the following two additional sustainability
components are identified (Muench et al.
2011):
• Extent – Extent represents the spatial and temporal
constraints and limits of the project-level system,
including such items as project length, right-of-way,
service life, height restrictions, construction working
hours, and so on. These constraints establish
the boundaries within which sustainability of the
project can be assessed.
• Expectations – Expectations are the key human
value constraints, which include both the economic
and social context, used to judge the overall performance
of the system. They may include performance
of individual design elements, the quality of
some aspect of the overall project, or how an outcome
beyond the project-level system is addressed.
Already, there has been modest movement within
the concrete paving industry to adopt practices that
support sustainability at the project level that have
broader system-wide sustainability impacts. For
example, a common technical nutrient used in concrete
production is slag cement, which is a byproduct
of another industry and improves the long-term properties
of concrete (meeting project-level constraints)
while reducing system-wide environmental impacts
(e.g., lowering the energy use and emissions of the
constructed pavement). Other recycled and industrial
byproduct materials (RIBMs) that are used in concrete
include fly ash, recycled concrete aggregate (RCA),
and air-cooled blast furnace slag, to name a few, all of
which are addressed in later chapters in this manual of
practice.
However, sustainability is much broader than the
application of a number of individual activities (such
as RIBM use). Focusing narrowly on individual activities
will result in minor improvements but will miss
out on the much greater opportunity to significantly
enhance the sustainability of the project-level system,
as well as positively impacting the system as a whole.
Without a guided and committed approach to implementation,
the adoption of sustainable practices by the
concrete pavement industry will languish. To move
sustainability from a philosophical concept to implementable
practices will require the adoption of the
following two additional components of sustainability
(Muench et al. 2011):
• Experience – Experience represents both what has
been learned and the ongoing learning process,
including technical expertise, innovation, and
knowledge of applicable historical information.
• Exposure – Exposure represents ongoing educational
and awareness programs for all stakeholders,
including the general public, agencies, engineering
professionals, and contractors.
The purpose of this manual of practice is to help meet
the objectives of these two sustainability components,
conveying industry experience and exposing stakeholders
in the concrete pavement industry to the
concepts and implementation of sustainable practices.
The next section of this chapter will introduce some
of the specific sustainable features of concrete pavements,
linking these features to the various phases
illustrated in Figure 2.3. Subsequent chapters expand
on each phase, providing actionable items that can be
implemented today and that will directly enhance the
project-level sustainability of concrete pavements.
2. Concrete Pavements
Many features of concrete pavements should be
assessed when considering them from a sustainability
perspective. Further, innovative features continue
to emerge that result in additional enhancement to
the sustainability of concrete pavements. Figure 2.4
illustrates a few of these features, each of which is
described in detail in subsequent chapters of this
manual of practice. The purpose of this section is to
describe the relationship between these features and
the life-cycle phases illustrated in Figure 2.3, as well
as among the features themselves. The complex nature
of these relationships demonstrates the need for the
application of a holistic systematic approach when
considering the sustainability of concrete pavement.
10 Ch. 2. PAVEMENT SUSTAINABILITY CONCEPTS Sustainable Concrete Pavements A Manual of Practice

Design Phase
It is fitting that the design phase is the first to be
discussed, as it is only through thoughtful and deliberate
design that sustainability can be achieved. Design
of concrete pavements has traditionally focused on
slab thickness design, although other design details,
including joint spacing and load transfer, slab support
considerations, drainage, and edge support to name
a few, have long been recognized as being of equal or
greater importance (Smith and Hall 2001).
These design details are directly considered in the
new AASHTO DARWin-ME Mechanistic-Empirical
Design Guide (MEPDG), which provides a rigorous
approach to considering the effect of multiple design
variables to assist in optimizing the design for given
conditions. Use of the MEPDG approach is growing
and will likely become the norm over time. Authorities
are developing local calibration data for the system or
using a locally modified version.
In addition to these traditional design considerations,
elements illustrated in Figure 2.4, including surface
texture, light color, long life, and improved storm
water quality can also be considered during the design
process. It is easy to see how these elements, although
selected at the design phase, interact directly with
other phases of the life cycle. For example, quiet
surface texturing, light pavement coloration, and
improved storm water quality (e.g., pervious concrete)
directly impact the use phase, particularly in an urban
environment where quiet and cool pavement surfaces
have positive social impacts and increased storm water
infiltration has broad economic, environmental, and
social benefits. Long-life pavements directly impact
preservation, rehabilitation, and reconstruction, delaying
the timing of future activities and reducing future
agency and user costs, thus directly affecting life-cycle
economic impacts while reducing future traffic delays
and associated environmental and social impacts. It
is also clear that design objectives cannot be achieved
if not integrated with the materials processing and
construction phases, thus necessitating collaboration
between the various specialties represented in typical
transportation agencies.
The design phase is also where innovative pavement
design types, such as two-lift concrete pavement,
roller-compacted concrete (RCC), precast concrete and
concrete pavers, and thin concrete pavement (TCP)
will be considered. The design phase is discussed in
detail in Chapter 3 of the manual of practice.
Materials
Material processing is a broad topic that includes
material acquisition, material processing, and concrete
mixture design and proportioning. Current material
acquisition is largely based on extractive industries,
such as mining aggregate or raw materials for cement
Figure 2.4 Features of concrete pavements that can enhance sustainability (from Wathne 2008)
Sustainable Concrete Pavements A Manual of Practice Ch. 2. PAVEMENT SUSTAINABILITY CONCEPTS 11

production. But some material acquisition is from
renewable resources (mainly for chemical admixtures),
and others are byproducts from other industries (e.g.,
RCA or supplementary cementitious materials such as
fly ash and slag cement). Material processing entails
taking the raw materials and making finished materials
including cement, crushed and blended aggregates,
admixtures, and so on. Material processing can often
be more energy intensive than construction activities,
meaning that small benefits in processing will lead
to substantial savings in the whole life cycle. Mixture
design and proportioning is the creation of material
blends that meet the engineering requirements and are
subsequently placed during the construction phase.
Materials have a major impact on all other life cycle
phases, as they often provide project-level constraints
during the design phase and strongly influence the
construction, preservation/rehabilitation, and reconstruction/recycling
phases, and even impact the operational
phase. Regarding sustainable features illustrated
in Figure 2-4, material processing factors most directly
influence decisions impacting the use of industrial
byproducts, reduced energy footprint, light color, and
long-life.
This phase is discussed in detail in Chapter 4 with
additional discussion on recycled concrete in Chapter 8.
Construction
The construction phase includes typical concrete plant
batching and mixing operations, transportation of
materials from stockpiles and the concrete plant, paving
operations, and post-paving activities. This phase
can have a large impact on the sustainability of the
concrete pavement over the life cycle because, even if
the best design and materials are used, poor construction
makes it unlikely that the concrete pavement will
achieve its design objectives or expected service life.
With respect to Figure 2.4, the construction phase
directly impacts long life, the creation of a quiet
surface texture, and low fuel consumption during
construction.
Concrete pavement construction is discussed in
Chapter 5, which briefly describes specific activities
that support enhanced sustainability, including low
energy plant operations, recycling water and returned
concrete, low-emission equipment, in-place recycling,
and local material utilization.
Operations
The operational or use phase of a concrete pavement
is rarely considered at the project level unless capacity
and congestion are being considered as part of a
transportation planning study. Yet, up to 85 percent
of greenhouse gas emissions associated with the
expected service life of a pavement can be incurred
during this phase (Ochsendorf 2010). This is most
significant on high-volume roads, where emissions
generated by vehicles are a dominant factor. To some
degree, it has been found that the rolling resistance of
vehicles moving on a rigid surface is less than that of
those moving on a flexible surface, but research is still
underway to determine the significance of this difference
and its impact on fuel efficiency and emissions.
What is known to be significant is that fuel efficiency
is improved on smooth roads, emphasizing the importance
of constructing smooth pavements and then
using preservation strategies that reduce roughness
(e.g., diamond grinding). These topics are discussed in
Chapter 6.
Sustainability attributes of the use phase that are
enhanced by the use of light-colored concrete surfaces
include improved night-time safety, reduced need for
artificial lighting, and reduced urban heat island effect.
Improved storm-water quality and quiet surfaces are
also benefits realized in the use phase in urban environments.
The urban environment also provides an
opportunity to use photocatalytic materials integrated
into the cement or applied as a coating to treat certain
harmful emissions. Such urban opportunities are discussed
in Chapter 9.
Preservation and Rehabilitation
Concrete pavement preservation is a strategy for keeping
good pavements in good condition. It is not only
economically cost effective but also has significant
environmental and social benefits. For one, preservation
strategies use limited amounts of new materials,
reducing the environmental burden of material extraction
and processing. Further, preservation techniques
entail minimal traffic disruption, reducing emissions
12 Ch. 2. PAVEMENT SUSTAINABILITY CONCEPTS Sustainable Concrete Pavements A Manual of Practice

and social impacts. And the use of diamond grinding
as a preservation strategy not only restores texture
to enhance safety, the resulting pavement surface is
quiet and smooth, reducing the impact of noise while
increasing fuel efficiency.
Preservation is no longer appropriate when the structural
capacity of the pavement needs to be improved.
At this point, a number of rehabilitation alternatives
can be effectively utilized, including the use of concrete
overlays. The appropriate and timely use of overlays
will take advantage of the remaining pavement
structural capacity, extending the pavement service
life in a cost-effective and environmentally beneficial
manner.
Concrete pavement renewal, which incorporates both
preservation and rehabilitation, is discussed in
Chapter 7.
Reconstruction and Recycling
The final stage of a concrete pavement’s life cycle
is reconstruction and recycling. In-situ recycling of
concrete pavement, generally as a new subbase or base
layer is a viable alternative, with the economic and
environmental advantages of minimal material transportation.
The use of screened RCA as a new base or
concrete is also a possibility. One benefit of crushing
concrete and exposing it to the atmosphere is that it
will sequester atmospheric carbon dioxide through
carbonation, an added benefit of recycling. Discussion
of these topics, along with the incorporation of
other recycled paving materials, including recycled
asphalt pavement (RAP), in new concrete pavement is
provided in Chapter 8, which focuses on completely
recycling the existing structure back into a newly
reconstructed pavement.
3. Importance of Innovation
One of the greatest advantages of adopting sustainable
concrete pavement practices is in the discovery of
things that are yet unknown. Considering economic,
environmental, and social factors over the entire pavement
life cycle will require a different way of thinking
about the concrete pavement industry. Current thinking
is driven by the need to meet only the short-term
economic bottom line. As this approach gives way to
longer-term thinking that considers all three facets
of sustainability, innovative solutions will emerge.
Implementing new, sustainable solutions can allow
the industry to move dynamically forward, realizing
multiple opportunities and expanding markets. In
contrast, if the industry (represented by all stakeholders,
whether owner or client) balks and is unable to
move beyond entrenched ideas and technologies, it
will be limited in its ability to recognize the opportunities
that exist.
Already, a number of technologies are being adopted in
response to implementing sustainability principles. As
discussed in Chapter 4, the most obvious are changes
in cementitious materials and mixture proportioning
that have significantly reduced the amount of portland
cement contained within a cubic yard of concrete.
This has led to a significant reduction in the carbon
footprint of paving concrete, with no anticipated
decrease in expected performance (many expect better
performance) and no increase in cost. Other innovations,
including the use of in-situ concrete recycling,
recycling water at the concrete plant, pervious concrete,
and next-generation quiet texturing, are already
becoming mainstream in some markets. Emerging
technologies including the use of photocatalytic
cements and the inclusion of RAP in concrete mixtures
are undergoing field trials in demonstration projects.
And, as described in Chapter 10, tools to rate the
sustainability of concrete pavements are also emerging
and will soon become integrated into common
practice.
Further advances are just over the horizon, whether
low-carbon to carbon-sequestering cements, innovative
designs or materials that result in a significant
reduction in pavement thickness, new bio-derived
admixtures that enhance the durability of concrete,
equipment that rapidly and efficiently recycles concrete
in-situ, next generation inexpensive and highly
efficient photocatalytic materials, or even pavements
that generate electricity to power adjacent neighborhoods.
Although the exact nature of these innovations
is speculative at this point, as is discussed in Chapter
11, it is a certainty that innovations are underway that
will change the nature of the concrete pavement industry
and that the adoption of these innovations will be
driven by sustainability principles.
Sustainable Concrete Pavements A Manual of Practice Ch. 2. PAVEMENT SUSTAINABILITY CONCEPTS 13

4. References
McDonough, W., and M. Braungart. 2002. Cradle to
Cradle: Remaking the Way We Make Things. New York,
NY: North Point Press.
Muench, S.T., J.L. Anderson, J.P. Hartfield, J.R. Koester,
M. Söderlund, et al. 2011. Greenroads Manual
v1.5. (J.L. Anderson, C.D. Weiland, and S.T. Muench,
Eds.). Seattle, WA: University of Washington. (www.
greenroads.org; accesses Dec. 5, 2011)
Ochsendorf, J. 2010. Life Cycle Assessment (LCA) of
Highway Pavements. Interim Report. Cambridge, MA:
Concrete Sustainability Hub, Massachusetts Institute of
Technology.
Senge, P., B. Smith, N. Kruschwitz, J. Laur, and S.
Schley. 2008. The Necessary Revolution: How Individuals
are Working Together to Create a Sustainable World. New
York, NY: Doubleday Publishing Group, New York.
Smith, K.D., and K.T. Hall. 2001. Concrete Pavement
Design Details and Construction Practices–State of the Art
Technical Digest. NHI Course No. 131060. Washington,
D.C.: National Highway Institute, U.S. Department of
Transportation.
Van Dam, T., and P. Taylor. 2009. Building Sustainable
Pavements with Concrete. Ames, IA: National Concrete
Pavement Technology Center, Iowa State University.
(www.cproadmap.org/publications/sustainability_briefing.pdf;
accessed Dec. 5, 2011)
Wathne, L. 2008. “Green Highways–Sustainability
Benefits of Concrete Pavement.” Presentation made
at the 45th Annual Concrete Paving Workshop of the
Iowa Chapter of the American Concrete Paving Association,
Des Moines, IA.
14 Ch. 2. PAVEMENT SUSTAINABILITY CONCEPTS Sustainable Concrete Pavements A Manual of Practice

Chapter 3
DESIGNING SUSTAINABLE
CONCRETE PAVEMENTS
Tom Van Dam
Sustainability is not an accident. Pavement design
plays a strong role in ensuring that the constructed
concrete pavement begins its life as a cradle-to-cradle
sustainable project. This chapter considers how concrete
pavement design plays a strong role in enhancing
the sustainability of concrete pavements. The chapter
begins by introducing the concept of context sensitive
design, which requires the designer to recognize
that a single approach to design does not meet all
needs, that input must be sought from the various
stakeholders, including those representing the natural
world, and that the design must be tailored to meet
the unique needs of every project. The state of the
practice in pavement design is then briefly introduced,
including designing for what is needed and avoiding
waste inherent in both under-design and over-design.
Specific concrete pavement design attributes that
enhance sustainability are then presented. Many of
these involve improving the interaction between the
pavement surface and the environment, whether using
specific textures that are quieter, lighter colors that
are cooler, patterns that are aesthetically pleasing and
safer, photocatalytics that have the ability to treat air
pollution, or pervious surfaces that have the ability to
improve storm water quality. The chapter concludes
with brief introductions to four innovative pavement
designs (two-lift, precast panels and pavers, rollercompacted
concrete, and thin concrete pavements)
that offer opportunities for the designer to further
enhance the sustainability of concrete pavements.

1. Context-Sensitive Design
Sustainability requires a thoughtful approach to concrete
pavement design. The designer must account for
human needs and values defined by the management
team and various stakeholders while considering the
environmental setting in which the pavement will be
constructed (Muench et al. 2011). This approach is
often referred to as context-sensitive design (CSD),
which entails meeting the needs of not only the user
but also the adjacent communities and the environment.
The key to successfully employing this principle
is recognizing that a single approach to design does
not meet all needs.
For example, the past practice of transversely tining
concrete pavements to create surface texture that
increased skid resistance and enhanced safety has been
demonstrated to have a significant impact on noise
generation through tire-pavement interaction (Rasmussen
et al. 2007). The noise issue was raised by communities
adjacent to roadways, and, in some cases,
concrete pavements were overlaid solely to reduce the
noise generated. Because of feedback from local communities,
research was conducted to identify factors
contributing to the objectionable noise and mitigation
strategies have been developed that have resulted
in safe and quiet concrete riding surfaces; see Figure
3.1(Rasmussen et al. 2008).
It is recognized that the same communities that object
to noise generated on a high-speed roadway may
have a different set of criteria for local, slow-speed
roads serving their neighborhoods. In such locations,
tire-pavement generated noise may be far less an issue
than aesthetics, high reflectivity, or surface drainage.
It is even possible that an urban neighborhood might
desire that roughness be designed into the surface to
produce a calming effect on vehicles exceeding the
speed limit, creating a safer and more livable community
for the residents. More information on urban
environments is given in Chapter 9.
Along the same lines, the needs in a rural environment
will differ from those of urban communities. Often,
the health of the “natural community,” which includes
flora and fauna and the quality of air and water, will
become increasingly important in rural settings. This
is why the designer must be sensitive to the context in
which the pavement is being designed.
Successfully implementing CSD requires early involvement
of everyone who is affected, including those representing
community interests and ecological systems,
through a collaborative, interdisciplinary approach.
Public involvement must be early and continuous.
Although this takes time and effort, it will result in
increased societal acceptance and reduced ecological
impact, improving project efficiency by reducing
expensive and time-consuming reworking of the project
at a later date.
In the end, designing to serve the community will
result in the construction of concrete pavement
projects that reflect a sense of the place where they
are built and that meld physically and visually within
the surrounding environment and community. More
detailed information on CSD can be found at
Figure 3.1 RoboTex scans of 100×200 mm samples showing variability of transverse tined surface and its
effect on noise level (adapted from Rasmussen et al. 2008)
16 Ch. 3. DESIGNING SUSTAINABLE CONCRETE PAVEMENTS Sustainable Concrete Pavements A Manual of Practice

www.contextsensitivesolutions.org. Specific activities
that can be immediately adopted to advance CSD for
concrete pavement design include the following:
• Involve key stakeholders – At the earliest stages of
design, involve key stakeholders in the process
to create a concrete pavement system that will
enhance the livability of the community. Stakeholders
include agency personnel and interested
organizations and community members, plus the
designer, materials suppliers, and contractor (if
possible). The Missouri Department of Transportation’s
(MoDOT) recently constructed US 141
“green” project in St. Louis, Missouri, illustrates
the power of stakeholder participation, involving
the contractor and community representatives in a
CSD process in designing a new route that passed
through a popular wooded area. By working with
the contractor and community, the designer was
able to incorporate multiple sustainable elements
into the design, allowing MoDOT to develop a
showcase project with strong community backing
(Jonas 2011).
• Take advantage of concrete’s versatility – Look for
opportunities to take advantage of concrete’s versatility
for creating highly functional, economical
pavements that also meet environmental and social
needs. Communities may be interested in concrete’s
ability to incorporate color and texture into aesthetically
pleasing patterns, enhance surface drainage,
demarcate pedestrian crossings, and provide highly
reflective surfaces.
2. Concrete Pavement Design:
The State of the Practice
The state of the practice in concrete pavement design
produces long-life pavements that withstand heavy
traffic and severe environmental loadings for decades
with little need for maintenance or rehabilitation
(Tayabji and Lim 2007, Hall et al. 2007). This ability
to confidently design pavements that will perform as
desired for 40 or more years is one of the most sustainable
inherent features of concrete pavements. Because
longevity is so important, it must be recognized that
long concrete pavement life is about a lot more than
just slab thickness. Common design features of longlife
concrete pavements include the following (Tayabji
and Lim 2007):
• Adequate structural slab thickness – Some designs
include additional thickness as a sacrificial layer
that will be removed during future diamond
grinding.
• Strong, erosion-resistant bases – Many states use
either asphalt- or cement-stabilized bases.
• Doweled transverse joints or continuously reinforced
concrete pavement – When jointed plain concrete
pavement design is used, the joint spacing is
relatively short, the joints are doweled, and often
highly corrosion-resistant dowels are used.
As discussed by Van Dam and Taylor (2009), a fundamental
principle in sustainable design is to design for
what you need. This means that the designer should
thoroughly understand the principles of pavement
design, accurately collect the required data, and use
the most advanced design tools available to ensure
that project needs are met within the given economic,
environmental, and social constraints. Overdesign—
in which the concrete slab is designed significantly
thicker than required—is wasteful, unjustifiably
increasing the economic and environmental burden of
the project. But under-design can be even more wasteful,
as it will often result in unacceptable performance,
premature failure, and the need to apply maintenance
and rehabilitation at an earlier than anticipated age at
great economic, environmental, and social cost.
The AASHTO DARWin-ME TM mechanistic-empirical
pavement design (MEPDG) approach more thoroughly
considers the contribution of material properties, support
conditions, climate, and traffic, as well as slab
geometry, edge support, and joint load transfer than
do empirically-based methods, thus resulting in more
accurate designs. Further, a mechanistic approach,
which is based on scientific principles, also accommodates
innovation much more readily than an empirical
approach, which relies on observation, experience,
or experiment, thus allowing the designer an avenue
to evaluate nontraditional approaches to design and
materials selection and proportioning.
Sustainable Concrete Pavements A Manual of Practice Ch. 3. DESIGNING SUSTAINABLE CONCRETE PAVEMENTS 17

As briefly discussed in Chapter 2, pavement design
must be approached holistically, with all design elements
considered together. In addition to the slab
thickness, other important design elements that must
be considered include material properties, joint spacing,
load transfer, drainage, supporting layers, and
surface texture (Smith and Hall 2001, Taylor et al.
2006).
3. Design Attributes Directly
Enhancing Sustainability
Depending on context, design attributes specifically
focused on enhancing sustainability should be considered.
These include such surface features as being
aesthetically pleasing, safe and quiet, reflective, and
photocatalytic.
As these design attributes are primarily applicable in
an urban environment (which is discussed in detail in
Chapter 9), they will only be briefly addressed here.
But the essential recognition from a design perspective
is how each of these features directly influences
the way the pavement interacts with the surrounding
community and/or ecological system, whether
through a reduction in noise, a safer riding surface,
improved aesthetics in the community, reduction in
air pollution, reduction of the heat island effect, and/
or reduction of run-off while improving storm water
quality. In fact, many of these features address multiple
needs. For example, photocatalytic materials not
only help breakdown nitrous and sulfur oxides (NOx
and SOx), they also are light colored, addressing the
urban heat island effect and perhaps improving storm
water quality as well (see Chapter 11).
The new generation of quiet surface textures are also
skid resistant, improving safety. Pervious concrete not
only improves storm water quality, it also is known to
reduce the heat island effect and, if used as a riding
surface, is known to be quiet. The use of concrete
pavements in heavy traffic locations such as bus
lanes and loading docks can be an effective means of
reducing pavement distress and the resulting effects
of closures for repairs. Thus, an informed designer
can package various pavement surface attributes to
address multiple sustainability goals. Further, these
attributes can be used in combination with some of
the emerging innovative design technologies discussed
next to great advantage.
4. Alternative and Emerging
Design Technologies
Traditionally, concrete pavement design has focused on
determining the thickness of a concrete slab, placed as
a single lift with one pass of a paver. Recently, a number
of alternative paving technologies have emerged
that are challenging this traditional way of constructing
concrete pavements, offering some unique design
opportunities including the following:
• Two-lift concrete pavement design – Two-lift pavements
are constructed in two lifts, wet on wet,
using two slipform pavers one immediately following
the other. The concrete mixture in the bottom
lift is often different from the mixture in the top lift.
• Precast concrete pavement systems – Fabricated off
site in precast plants, this type of pavement can
offer a number of sustainability enhancements.
• Interlocking concrete pavers – Also fabricated off site
in a precast plant, pavers provide an aesthetically
pleasing surface that can also be pervious, highly
reflective, or even incorporating photocatalytics for
use in streets and local roads.
• Roller-compacted concrete (RCC) pavements – RCC
pavement designs use stiff concrete mixtures placed
and densified using equipment typical of hot-mix
asphalt (HMA) construction. Traditionally used in
hydraulic structures, pavement in industrial facilities,
and cargo handling areas, it is starting to be
used in streets and local roads.
• Thin concrete pavement (TCP) design – Based on a
patented Chilean design, TCP is characterized by
relatively thin slabs with short joint spacing.
• Pervious pavements – Pervious pavements allow
rainwater to percolate and replenish groundwater
rather than requiring rainwater to be handled by a
storm water or effluent system.
The following sections briefly discuss each of these
innovations and how they can be used in the design of
sustainable concrete pavements.
18 Ch. 3. DESIGNING SUSTAINABLE CONCRETE PAVEMENTS Sustainable Concrete Pavements A Manual of Practice

Two-Lift Concrete Pavement
Two-lift concrete paving is not new. In fact, the oldest
concrete pavements in the United States, constructed
by the R.S. Blome Granitoid Co., were placed as twolifts,
wet-on-wet, with the top lift being a different
concrete than the bottom lift. Two-lift construction
was also used to facilitate the placement of reinforcing
mesh in jointed reinforced concrete; the mesh
was set upon the surface of the bottom lift and encapsulated
by the top lift. Recently, after examining the
excellent performance of two-lift concrete pavements
in Europe, there has been a resurgence of interest in
adopting modern two-lift concrete pavement design in
the United States, as shown by recent demonstration
projects constructed in Kansas and Missouri (see www.
cptechcenter.org/projects/two-lift-paving/index.cfm).
This pavement system typically consist of a thick
bottom lift (typically 80 percent or more of the total
thickness) and a thin (20 percent or less of the total
thickness) top lift that is optimized for carrying traffic.
Many European countries utilize an exposed aggregate
surface texture in conjunction with the two-lift construction
process.
The potential sustainability advantages of two-lift
pavement include the following:
• Bottom lift – The concrete mix proportions for the
bottom lift can be optimized knowing it will be
protected from the elements during construction
(as it will be capped with the top lift) and will not
be subjected directly to traffic. This means that it
can use a higher supplementary cementitious material
(SCM) content, higher percentage of recycled
aggregate including recycled asphalt pavement
(RAP), and aggregates with less stringent requirements
(e.g., wear resistance) than normal because
the bottom lift will not be exposed to traffic. A
broader range of locally available aggregates and
higher amounts of recycled and industrial byproduct
materials (RIBMs) can be used, and so reduce
the environmental footprint of the concrete.
• Top lift – The relatively thin top lift is optimized
to carry traffic. It often uses wear-resistant aggregate
that may have to be transported longer distances
and a higher portland cement content,
but can do so without significantly impacting the
environmental footprint of the pavement due to the
thinness of the layer. This ensures good long-term
durability and a safe riding surface, especially if the
thickness of the top lift is designed for multiple diamond
grindings over its life. In the case of the Kansas
demonstration project, the use of an exposed
aggregate surface was investigated to reduce noise
generated from tire-pavement interaction (Shields
and Taylor 2009). The Missouri project is experimenting
with the use of photocatalytic cement in
the top-lift (www.cptechcenter.org/t2/documents/
EnvironmentalIssues-Stone.pdf) to treat air pollution.
Photocatalytic materials are expensive, and
thus using them only in the top lift makes sense to
reduce costs without impacting performance.
Experience with two-lift paving in the United States
is limited but increasing. Eleven two-lift projects were
constructed from 1970 to 1994 (Florida, Iowa, Kansas,
Michigan, and North Dakota) (Harrington et al. 2010)
all are still in service. In 2008, the Kansas DOT constructed
over five miles of two-lift pavement on I-70
west of Abilene (Figure 3.2).
The versatility inherent in the two-lift design provides
the designer with multiple options to cost effectively
integrate one or more sustainable attributes into the
new pavement, resulting in economic savings while
improving environmental and social performance. It is
expected that this versatility will result in the widespread
adoption of this technology in the future.
Figure 3.2 Two-lift pavement being constructed in
Kansas
Sustainable Concrete Pavements A Manual of Practice Ch. 3. DESIGNING SUSTAINABLE CONCRETE PAVEMENTS 19

Precast Concrete Pavement Systems
Precast concrete pavement systems have a long history,
but with recent innovations they will continue to
grow in popularity. Precast concrete pavement systems
typically consist of individual panels that are one to
two lanes in width and 10 to 15 ft in length, depending
on the system. The pavement panels are produced
in a precast plant, where the material is proportioned,
molded, consolidated, and cured under controlled
conditions, then shipped to the site where they are
assembled on grade.
Fabrication under controlled conditions eliminates
a major construction variable—unfavorable ambient
weather conditions—which can play havoc on
conventionally cast-in-place concrete pavements, and
it also reduces material and construction variability.
Further, precast concrete pavement systems allow the
cost-effective implementation of certain sustainability
features, including enhanced aesthetics, specialty
surface textures, high surface reflectivity, and photocatalytic
materials. Many of these features are made
possible because the pavement wearing surface can
be cast against a mold in two (or more) lifts if desired,
giving a degree of control that is not possible with castin-place
pavements. Casting the surface against a mold
also results is a denser surface, as the lighter concrete
mixture constituents (air and water) rise towards what
will be the underside of the pavement and the dense
cement and aggregate settle to form a dense molded
surface.
Initial work in this area focused on the use of precast
panels to rapidly install full-depth repairs in jointed
concrete pavements (Tayabji and Hall 2008). This
repair method continues to be used in a number of
states, where full-lane width panels are cast in two to
three standard lengths, stockpiled, and then rapidly
inserted into a gap cut to the specified size in the damaged
pavement; see Figure 3.3.
in length, and similar to a conventionally designed
concrete pavement in thickness. Although there are
multiple variations of this type of system, in one of
the most common systems the panels are placed on
a meticulously prepared surface with bedding grout
used to ensure uniform slab support. Load transfer
devices, embedded using non-shrink, high-strength
grout inserted after placement, are used to establish
composite slab action across joints (Fort Miller Co.
2011).
• Precast prestressed concrete pavement system (PPCPS)
– These systems typically consist of rectangular
precast slabs that are up to two lanes (38 ft) in
width, 10 ft in length, and thinner than conventionally
designed concrete pavements, with a
thickness of 7 to 8 in. for highway applications.
They are prestressed in the transverse direction
during fabrication and placed in 150- to 250-ft long
pavement segments that are post-tensioned longitudinally
during construction. Plastic sheeting is
used to separate the panels from the base, allowing
movement of the panels during the post-tensioning
operation. The use of prestressing/post tensioning
increases load capacity, maximizing pavement life
(Merritt and Tayabji 2009).
Regardless of the system employed, precast pavements
have some unique features that can enhance sustainability.
First, when used either as a full-depth repair or
as an entire pavement system, a well executed precast
pavement installation can be done with minimal
disruption to traffic because there is no need to wait
Current emphasis is on the implementation of precast
panels to create entire pavement systems. The following
two basic approaches are currently used in the
United States (FHWA 2011):
• Jointed precast concrete pavement system (JPCPS) –
These systems typically consist of rectangular precast
panels that are one lane in width, 10 to 15 ft
Figure 3.3 Precast pavement being installed
(photo courtesy of Shiraz Tayabji, FHWA)
20 Ch. 3. DESIGNING SUSTAINABLE CONCRETE PAVEMENTS Sustainable Concrete Pavements A Manual of Practice

for the concrete to gain adequate strength prior to
opening to traffic. This is most significant for repairs in
urban areas but is also true for full-lane replacements
if staged correctly. Minimizing traffic disruption has
many positive effects, including reduced user costs
incurred due to delay and corresponding increased
fuel consumption, reduced environmental damage
from increased emission associated with vehicles
slowed by congestion, and reduced social impacts to
surrounding communities from noise and gridlock.
Second, precast systems are anticipated to have long
lives that are relatively maintenance free. The sustainability
advantages of long-life pavements have already
been discussed in Chapter 2, but in summary they
include the following:
• Reduced life-cycle economic cost.
• Reduced life-cycle environmental impact due to less
need for extracted materials and for future rehabilitation
and reconstruction.
• Reduced traffic delay and congestion during construction
and over the life cycle.
The advantages of using two or more lifts and casting
the pavement surface against a mold can be capitalized
on in precast pavement systems, optimizing the
surface for the given application. For a pavement carrying
high-speed traffic, the surface can be designed to
be exceptionally quiet while providing good frictional
characteristics to enhance safety. For slower speed
pavements designed for the urban environment, the
surface can be designed to be aesthetically pleasing,
cool, photocatalytic, and drainable and even to provide
a “traffic calming” effect by inducing nuisance
vibration in vehicles operating too quickly. Further,
precast pavement systems for the urban environment
can be designed to “snap in and snap out,” meaning
that the precast panel over a needed utility repair is
simply detached and removed, the repair to the utility
completed, and the panel reattached. This eliminates
waste, expedites the repair process, and maintains the
integrity of the pavement system. It is easy to envision
the ability to design a major urban project, such as an
intersection replacement, using a precast pavement
system in which all the design, fabrication, and staging
are done ahead of time and the work is completed over
a few evenings or a weekend.
Roller-Compacted Concrete Pavement
Roller-compacted concrete (RCC) pavement has been
used in the construction of various types of civil infrastructure,
including dams, other hydraulic structures,
cargo handling facilities, and pavements. Although
the constituents in RCC are similar to conventional
concrete, they differ in proportioning, with RCC typically
having less cementitious material and an aggregate
gradation similar to that used in hot-mix asphalt
(HMA) mixtures. In a fresh state, RCC is very stiff and
is thus placed using construction methods similar to
those used for HMA construction, using an HMA-type
paver and compacted by heavy vibratory steel drum
and rubber-tired rollers (Figure 3.4). Ultimate loadcarrying
capacity is obtained through a combination
of internal, aggregate-to-aggregate friction and the
cohesion obtained through hydration of the binder.
The final surface is adequate for pavements carrying
traffic at low and moderate speeds but often is either
diamond ground or overlaid to meet the smoothness
demands of high-speed traffic. An excellent guide on
RCC pavements has been written by Harrington et al.
(2010), and additional information is provided by the
Portland Cement Association (PCA 2011).
RCC shares many sustainability attributes with conventional
concrete pavements, including low lifecycle
economic costs, the ability to incorporate a
high amount of RIBMs into the mix, and high surface
reflectivity. Some of the specific advantages of RCC
from a sustainability perspective include low initial
cost and rapid construction compared to both conventionally
designed concrete pavements and multi-lift
HMA pavements of similar structural capacity. In addition,
if the lower cementitious content translates into a
lower portland cement content, the carbon footprint is
Figure 3.4 RCC pavement being placed (photo
courtesy of PCA)
Sustainable Concrete Pavements A Manual of Practice Ch. 3. DESIGNING SUSTAINABLE CONCRETE PAVEMENTS 21

reduced. Load transfer across joints may be lower than
conventional concrete because dowels are not used.
As another arrow in the quiver for designers of sustainable
concrete pavements, the use of RCC as a paving
material will likely continue to grow.
Interlocking Concrete Pavers
Similar to precast concrete pavement systems, interlocking
concrete pavers are also produced in a plant,
where the material is proportioned, pressed, and cured
under controlled conditions, then shipped to the site
where they are assembled on grade. Again, fabrication
under controlled conditions eliminates a major construction—unfavorable
ambient weather conditions—
which can play havoc on conventionally cast-in-place
concrete pavements, and it also reduces material and
construction variability..
Pavers are the original pavement surfacing material,
with the use of stone pavers dating back to antiquity.
Modern interlocking concrete pavers have evolved
to be extremely versatile and durable and are used in
projects as varied as low-volume parking areas to the
most heavily loaded cargo handling facilities. Figure
3.5 shows an example of permeable interlocking
concrete pavers, which not only possess the necessary
structural capacity and long-term durability for
the application but also are aesthetically pleasing
while effectively managing surface run-off. Vehicular
interlocking concrete pavers, such as those shown
in Figure 3.6, can carry mainline traffic. They are
particularly applicable in urban areas where both
their attractive appearance and versatility to permit
maintenance of underground utilities can be used to
good advantage.
Recent innovations have led to the installation of
interlocking concrete pavers in Chicago that have a
thin photocatalytic surfacing. The high reflectivity of
these pavers will help mitigate the urban heat island
effect. The photocatalytic surface will help keep the
surface bright white while also treating nitrous and
sulfur oxides. Automated methods have been developed
in Europe that expedite the placement of interlocking
concrete pavers, significantly accelerating the
construction process. Additional information regarding
interlocking pavers, including using them to support
sustainable design, can be found at the website of the
Interlocking Concrete Pavement Institute (www.icpi.org/).
Thin Concrete Pavement Design
Most of the design technologies discussed so far (e.g.,
two-lift, precast, pavers, and RCC) have been around
for decades and are experiencing something like a
revival due to their implications for sustainability.
Thin concrete pavement (TCP) design, however, is
Figure 3.5 Permeable interlocking concrete paver
blocks make an aesthetically pleasing, well-drained
pavement for low-volume streets and parking lots
(photo courtesy of Interlocking Concrete Pavement
Institute)
Figure 3.6 Vehicular interlocking concrete pavers
being placed in a historic downtown area (note
the use of colored concrete to provide a visual
offset for the crosswalk) (photo courtesy of Tom Van
Dam, CTLGroup)
22 Ch. 3. DESIGNING SUSTAINABLE CONCRETE PAVEMENTS Sustainable Concrete Pavements A Manual of Practice

truly new and has yet to gain widespread acceptance
in North America. TCP design originates in Chile
(Covarrubias and Covarrubias 2007 and is still under
evaluation there as well as in a number of other countries.
In North America, considerable work has been
conducted at the University of Illinois with very promising
results (Cervantes and Roesler 2009).
The basic concept is simple. Stresses are generated in
concrete slabs through a combination of traffic and
environmental loads. The larger the concrete slab,
the more truck axles it will carry at one time and the
higher the stress incurred due to temperature and
moisture gradients. Over time, the repeated stresses
generated by the combination of traffic and environmental
loading will result in fatigue cracking of the
slab. By reducing slab size to a square with the dimensions
of one-half a lane (6 ft by 6 ft), the stresses generated
are significantly reduced to the point that slab
thickness can be reduced by almost half. The reduction
in slab thickness will be accompanied by higher
deflections; thus the need for good base support that
resists pumping and erosion is emphasized (Cervantes
and Roesler 2009).
The promise of TCP design is that the reduction in
slab thickness will substantially reduce the economic
and environmental costs of concrete pavements. Slab
thickness of as little as 4 to 6 inches may be all that is
required to carry moderate to heavy traffic volumes,
and early results indicate that there is no need for
embedded steel load transfer devices.
5. References
Cervantes, V., and J. Roesler. 2009. Performance of Concrete
Pavements with Optimized Slab Geometry. Research
Report ICT-09-053. Urbana, IL: Illinois Center for
Transportation. University of Illinois. (http://ict.illinois.
edu/publications/report%20files/ICT-09-053.pdf;
accessed Dec. 5, 2011)
Covarrubias, J.P.T., and J.P.V. Covarrubias.
2007. TCP–Thin Concrete Pavements. (http://siteresources.worldbank.org/INTTRANSPORT/
Resources/336291-1153409213417/TCPavementsPaper.pdf;
accessed Dec. 5, 2011)
Federal Highway Administration (FHWA). 2011. Innovations–Precast
Concrete Pavement Systems. (www.fhwa.
dot.gov/hfl/innovations/precast.cfm; accessed Dec. 5,
2011)
Fort Miller Co., Inc. 2011. Super-Slab®. (www.superslab.com/;
accessed Dec. 5, 2011)
Hall, K., D. Dawood, S. Vanikar, R. Tally, Jr., T.
Cackler, et al. 2007. Long-Life Concrete Pavements
in Europe and Canada. Washington, D.C.: FHWA.
FHWA-PL-07-027.
Harrington, D., F. Abdo, W. Adaska, and C. Hazaree.
2010. Guide for Roller-Compacted Concrete Pavements.
SN298. Ames, IA: National Concrete Pavement Technology
Center, Iowa State University.
At this juncture, a number of test sites are being constructed
to investigate TCP designs, but a major barrier
to implementation is that this is a patented technology,
thus giving most DOTs pause in considering it for
adoption.
Pervious Concrete
An approach to reducing the amount of water runoff
from hard surfaces is to build pervious pavements
for parking lots and low speed roadways; see Figure
3.7. Pervious pavements allow water to seep into the
ground, thereby recharging groundwater and allowing
natural processes to treat it instead of having to build
extensive treatment works. This design alternative is
discussed in detail in Chapter 9.
Figure 3.7 Pervious concrete being placed (photo
courtesy of John Kevern, University of Missouri-
Kansas City)
Sustainable Concrete Pavements A Manual of Practice Ch. 3. DESIGNING SUSTAINABLE CONCRETE PAVEMENTS 23

Jonas, J. 2011. “Route 141 “Green” Project in St.
Louis, MO.” Presentation made at the MO/KS Chapter,
American Concrete Pavement Association, 31st Annual
Portland Cement Concrete Conference, Kansas City,
MO.
Merritt, D., and S. Tayabji. 2009. Precast Prestressed
Concrete Pavement for Reconstruction and Rehabilitation
of Existing Pavements. Washington, D.C.: FHWA.
FHWA-HIF-09-003.
Muench, S.T., J.L. Anderson, J.P. Hartfield, J.R. Koester,
M. Söderlund, et al. 2011. GreenroadsManual
v1.5. (J.L. Anderson, C.D. Weiland, and S.T. Muench,
Eds.). Seattle, WA: University of Washington. (www.
greenroads.org; accesses Dec. 5, 2011)
Portland Cement Association (PCA). 2011. Roller-Compacted
Concrete. (www.cement.org/pavements/pv_rcc.
asp; accessed Dec. 5, 2011)
Rasmussen, R.O., R. Bernhard, U. Sandberg, E. Mun.
2007. The Little Book of Quieter Pavements. Washington,
D.C.: Federal Highway Administration. FHWA­
IF-08-004. (www.tcpsc.com/LittleBookQuieterPavements.pdf;
accessed Dec. 5, 2011)
Rasmussen, R.O., S.I. Garber, G.J. Fick, T.R. Ferragut,
and P.D. Wiegand. 2008. How to Reduce Tire-Pavement
Noise: Interim Better Practices for Constructing and Texturing
Concrete Pavement Surfaces. TPF-5(139). Ames,
IA: National Concrete Pavement Technology Center,
Iowa State University. (www.cptechcenter.org/publications/cpscp-interim.pdf;
accessed Dec. 5, 2011)
Shields, S., and P. Taylor. 2009. “Working a Double
Lift: Two-Lift Paving Makes a Comeback in the U.S.”
Roads and Bridges. (www.roadsbridges.com/workingdouble-lift;
accessed Dec. 5, 2011)
Tayabji, S., and S. Lim. 2007. Long-Life Concrete
Pavements: Best Practices and Directions from the States.
Washington, D.C.: FHWA. FHWA-HIF-07-030.
(www.fhwa.dot.gov/pavement/concrete/pubs/07030/;
accessed Dec. 5, 2011)
Tayabji, S., and K. Hall. 2008. Precast Concrete Panels
for Repair and Rehabilitation of Jointed Concrete
Pavements. Washington, D.C.: FHWA. FHWA­
IF-09-003. (www.fhwa.dot.gov/pavement/pub_details.
cfm?id=628; accessed Dec. 5, 2011)
Van Dam, T., and P. Taylor. 2009. Building Sustainable
Pavements with Concrete. Ames, IA: National Concrete
Pavement Technology Center, Iowa State University.
(www.cproadmap.org/publications/sustainability_briefing.pdf;
accessed Dec. 5, 2011)
24 Ch. 3. DESIGNING SUSTAINABLE CONCRETE PAVEMENTS Sustainable Concrete Pavements A Manual of Practice

Chapter 4
SUSTAINABLE CONCRETE PAVEMENT
MATERIALS
Peter Taylor
Tom Van Dam
The materials used in making paving concrete have
a significant impact on the sustainability of the pavement.
This chapter details the importance of using
materials that result in durable, long-lasting concrete
that withstands traffic loadings and climate during its
service life. The chapter primarily focuses on cementitious
materials, because of their environmental impact
as part of mixture design. The discussion emphasizes
the need to use the appropriate amount of cementing
materials by reducing unwarranted cement and using
conventional supplementary cementitious materials
(SCMs), including fly ash and slag cement. The
emergence of lower energy, lower emissions cements,
including blended cements, portland-limestone
cements, geopolymers, and carbon neutral/sequestering
cements, is also discussed. The chapter concludes
with a discussion of other concrete ingredients, with
specific emphasis on the use of recycled and industrial
byproduct materials used as aggregate.

1. Cementitious Materials
It is well established that the manufacturing of portland
cement (specified under AASHTO M 85/ASTM C
150) is an energy intensive process, involving heating
large quantities of finely ground rocks and minerals to
very high temperatures (roughly 1400°C) to produce
nodules called clinker that are then interground with
gypsum to a fine powder; see Figure 4.1. In addition,
the carbon dioxide (CO 2 ) burden is high because
the process includes decomposing calcium carbonate
(CaCO 3 ) rock into calcium oxide (CaO) and CO 2 .
Roughly half of the CO 2 generated comes from this
source, and the proportion is increasing as manufacturers
make their process more energy efficient (Van
Dam and Taylor 2009). The generation of CO 2 through
the cement manufacturing process is illustrated in
Figure 4.2 (Van Dam et al. 2010).
The amounts of energy required and CO 2 produced
depend on the age and efficiency of the manufacturing
plant. Many older plants use a wet process that
includes drying the materials from slurry. Many of
these plants have closed in the United States as a
result of economic pressures and because newer, more
efficient dry-process facilities have come on line. The
FHWA INVEST tool gives credit for cement supplied
from efficient Energy Star® plants (see Chapter 10).
Approximately 0.8 to 1.0 tons of CO 2 are produced
per ton of cement (Hanle et al. ND, Van Dam and
Taylor 2009), with the U.S. national average currently
listed as 0.927 tons of CO 2 equivalent produced per
ton of cement (NREL 2011).
In 2008, the total U.S. greenhouse gas (GHG) emissions
were estimated at 7 billion metric tons of CO 2
equivalent, 40 million tons (about 0.6 percent) of
which were generated through the manufacturing of
portland cement (EPA 2010). This is compared to 5
to 7 percent reported for the rest of the world (Malhotra
2000). The lower figure for the United States
reflects the facts that cement manufacturing in the
United States is becoming more efficient and that the
American way of life generates considerably more CO 2
equivalents in sectors other than cement manufacturing
compared to the rest of the world.
Roughly 2.8 billion tons of cement is consumed
annually worldwide (WBCSD 2010), which equates
to approximately 800 lb of cement per person per
year. While the impact tied to manufacturing portland
cement is relatively high, it must be remembered that
relatively little cement is used in a concrete mixture—normally
12 to 15 percent by mass in pavement
mixtures. The other constituent materials (aggregate,
water, SCMs, and admixtures) typically have very little
energy or CO 2 impact associated with them, thus making
concrete a reasonably efficient material as a whole.
For example, the 800 lb of cement per person per
year discussed previously would make roughly 5,600
lb of concrete, making concrete the most commonly
used building material on the planet with only water
being used in greater amounts. Concrete is literally the
foundation upon which modern civilization is built.
Figure 4.1 A cement kiln (photo courtesy of PCA)
Figure 4.2 CO 2 generation in cement
manufacturing (Van Dam et al. 2010)
26 Ch. 4. SUSTAINABLE CONCRETE PAVEMENT MATERIALS Sustainable Concrete Pavements A Manual of Practice

Work is ongoing to quantify the life-cycle environmental
impact of pavement materials, including concrete
(MIT 2010).
Although the global impact of cement manufacturing
on GHG emissions is large, it must be remembered
that the burdens can be reduced by any combination
of four actions:
• Reduce the energy and GHG emissions associated
with portland cement clinker production.
• Reduce the amount of portland cement clinker in
the cement.
• Reduce the amount of cement in the concrete
mixture.
• Use concrete more efficiently in a pavement over
the life cycle.
Each of these is discussed in following sections.
More Efficient Clinker Production
The manufacturing process for cement is continually
being improved and made more efficient by the use
of more efficient kilns, more efficient grinding equipment,
optimized transportation, and modified process
control. The use of alternative fuels including tires and
bio-fuels helps reduce the combustion of nonrenewable
resources while removing them from the waste
stream (PCA 2009). Burning hazardous organic waste
such as solvents and oils in cement kilns is beneficial
not only because it reduces the amount of fossil
fuel combusted but also because the extremely high
temperatures decomposes them completely, rendering
them non-hazardous (Basel Convention 2009).
Reducing Portland Cement Clinker in
Cement
Reducing the portland cement clinker content in
the cement directly reduces the GHG emissions and
energy consumption associated with cement manufacturing.
Portland cement can be supplemented in
concrete mixtures with the use of so-called supplementary
cementitious materials (SCMs) and/or with
finely ground limestone. SCMs are largely byproducts
from other industries, such as the burning of pulverized
coal at power plants or the production of iron
from ore in a blast furnace, but can also be produced
from natural materials such as clay. These processes
also result in GHG emissions and energy consumption
but at lower rates than clinker production.
SCMs chemically and physically complement the
hydration of portland cement, often resulting in more
durable concrete. Hydration of portland cement produces
calcium silicate hydrate (C-S-H) that provides
the backbone of strength and impermeability of the
cementitious system. But portland cement hydration
also produces calcium hydroxide (CaOH), a crystalline
material; see Figure 4.3. Calcium hydroxide
contributes little to strength or impermeability. Most
SCMs contain glassy silica and aluminate phases that
react with the calcium hydroxide to form more C-S-H
and/or calcium silica aluminate hydrate (C-S-A-H),
enhancing the long-term performance of the concrete
mixture. The types of commonly used SCMS are discussed
in more detail in a later section.
Another approach to reduce consumption of nonrenewable
resources while reducing waste destined for
landfills is the use of industrial byproducts such as fly
ash (Bhatty, 2006), foundry sand, slag, mill scale, and
cement kiln dust as raw feed.
Work is ongoing to identify means of making cement
manufacturing more efficient by modifying its molecular
composition. This work is likely to take several
years to find its way into everyday practice.
Figure 4.3 Scanning electron micrograph of C-S-H
and CaOH crystals (Kosmatka and Wilson 2011)
Sustainable Concrete Pavements A Manual of Practice Ch. 4. SUSTAINABLE CONCRETE PAVEMENT MATERIALS 27

One or more SCMs can be included in the cement by
inter-grinding with the clinker or by blending with
cement at the cement plant, in which case they are
sold as blended cements under AASHTO M 240/ASTM
C 595. Alternatively, it is common to blend the SCMs
with the cement and other concrete ingredients at the
batch plant.
Under existing U.S. standards for plain portland
cement (AASHTO M 85/ASTM C 150), the system
may contain up to 5 percent ground limestone as well
as up to 5 percent inorganic processing additions. In
practice, the amount of ground limestone and inorganic
processing additions are less, limited by the losson-ignition
(LOI) requirement. The standards impose
limitations to ensure that the performance of such
materials is not reduced. Consideration is being given
to increasing the amount of permitted ground limestone
as in Canada and Europe (Hooton et al. 2007).
Specifications exist for both blended and performance
cements (Van Dam and Smith 2011). Blended
cements are described under AASHTO M 294/ASTM
C 595, which impose limits and requirements on
the source and performance of all of the ingredients.
These cements are a blend of portland cement and
one or more SCMs. Ternary cements containing two
SCMs can also be created at the batch plant by blending
more than one SCM, a practice often used to
address side effects of one SCM through the inclusion
of another SCM. Extremely efficient mixtures can be
prepared using such systems (Tikalsky 2007). However,
it has been noted that batch plant–created ternary
mixtures require expertise and close attention to detail,
dictating the need for a high level of quality control.
In addition to blended cements, ASTM C 1157 is a
“performance” standard for hydraulic cements that
has no requirements regarding the composition of the
cement but instead imposes performance limits. ASTM
C 1157 cements with 10 percent limestone have been
produced and used successfully on pavement projects
in several states (Hooton 2009, Van Dam et al. 2010).
Reducing Cementitious Contents in
Concrete
Many specifications require that a minimum amount
of cementitious material (or portland cement) be used
in paving concrete (e.g., a traditional concrete paving
mixture may require a minimum six-sack mix, which
is equivalent to 564 lb/yd 3 concrete). This minimum
cement content requirement may have been appropriate
before the common use of chemical admixtures
and the adoption of optimized aggregate grading, but
may no longer be relevant using today’s concrete and
paving technologies.
Performance of a mixture is fundamentally controlled
by the water-to-cementitious-materials (w/cm) ratio as
long as there is sufficient paste in the mixture to fill the
voids between the aggregate particles and to separate
the aggregate particles so that they will flow past each
other in the fresh state. However, workability can be
improved with the use of admixtures, within limits,
and by reducing paste demand through use of an optimized
aggregate gradation that contains coarse, intermediate,
and fine particles (Taylor et al. 2006). As long
as the concrete is workable and is placed with good
consolidation, long-term performance will generally be
improved by reducing the cementitious content. This
means that paving mixtures can be made with lower
cementitious contents than the traditional six-sack
concrete mixture without compromising engineering
performance. Education, investment in additional
aggregate bins, and improved quality assurance may be
necessary to reduce the risk of failures.
Reduce Concrete Used Over the Life
Cycle
All things equal, sustainability is improved by reducing
the amount of concrete used for a given application.
But it is essential that this is considered over the life
cycle of the pavement, and not just in the short term.
Two essential elements to accomplish this are appropriate
design (as discussed in Chapter 3) and the use
of durable concrete materials.
With regards to the former point, there is short-term
economic and environment-related pressure to reduce
the thickness of concrete pavements, lowering both
the initial cost and the environmental footprint. The
use of improved design methodologies and appropriate
design details (e.g., proper joint spacing, load
transfer devices, quality base, and so on) can accomplish
this without compromising long-term structural
performance. But it is essential that this be done with
28 Ch. 4. SUSTAINABLE CONCRETE PAVEMENT MATERIALS Sustainable Concrete Pavements A Manual of Practice

caution, as thickness correlates with structural capacity,
and arbitrarily using thinner concrete will likely
compromise one of the benefits of using a concrete
pavement, which is the potential to provide many
years of low-maintenance service. Specifying a concrete
thickness insufficient to carry traffic over the
design life can have large negative impacts on sustainability
(economic, environmental, and social), not only
because the pavement will need to be replaced sooner
than anticipated but also because of traffic delays during
repeated repair and reconstruction. The counter to
this is that innovative design may result in significantly
improved sustainability even if the short-term initial
economic and environmental costs are slightly higher.
This is why it is essential that a life-cycle approach be
taken when evaluating design changes.
One of the hallmarks of concrete pavement is its
legendary longevity. It is reasonable to assume that
a properly designed concrete pavement will meet
or exceed its design life. It is also known that pavements
can prematurely fail even if they are structurally
adequate. To address this, in addition to proper design,
all the other stages—material selection, construction,
and maintenance—have to be adequate and appropriate
to ensure longevity. From a cementitious materials
perspective, it is paramount that the right materials are
selected and proportioned correctly for the environment
to which the pavement will be exposed (Taylor
et al. 2006). Other factors that need to be considered
are the effects that the cementitious materials selection
will have on the surface characteristics of the pavement
leading to changes in reflectivity, which contributes
both to the albedo (e.g., urban heat island effect) and
night-time safety as discussed in Chapter 9.
Fly ash is a byproduct of burning pulverized coal for
the generation of electrical power. The rock embedded
in the coal melts in the furnace and is carried up the
stack in the flue gases. As it rapidly cools, small glassy
spheres are formed that are collected before the flue
gases are emitted to the air; see Figure 4.4. Because
of the small size, glassy form, and chemical composition
of the ash, it dissolves and reacts with the cement
paste to contribute to the performance of the mixture.
About 63 million tons of fly ash were produced in the
United States in 2009, of which about 12 million tons
were used either to make cement or in concrete (ACAA
2009).
Fly ash is currently specified in AASHTO M 295/ASTM
C 618 in two classes based on the chemical composition.
The differences are generally influenced by the
source of the coal. In general, Class C fly ash is higher
in lime content (CaO) and tends to be more reactive
at early ages than Class F. The higher CaO content is
beneficial for early strength gain but can have negative
effects on alkali-silica reactivity and sulfate resistance.
It should be noted that the specification for fly ash is
broad and that two ashes from different sources, albeit
of the same class, are likely to perform very differently;
therefore, performance testing should be conducted to
determine if the chosen fly ash is behaving as desired
(Taylor et al. 2006).
Dosage of fly ash is typically between 15 and 40 percent
by mass of cement. The amount of fly ash that can
2. Supplementary Cementitious
Materials
As discussed above, most SCMs are byproducts from
other industries that beneficially react with portland
cement to enhance the performance of concrete. The
effective use of SCMs reduces not only the amount of
portland cement required but also the need to dispose
of what otherwise would be industrial waste.
The two most commonly used SCMs in paving concrete
are fly ash and slag cement.
Figure 4.4 Backscatter electron image of fly ash
particles (Kosmatka and Wilson 2011)
Sustainable Concrete Pavements A Manual of Practice Ch. 4. SUSTAINABLE CONCRETE PAVEMENT MATERIALS 29

be used is often limited by concerns of delayed setting
times and lower early strength gain. In some cases,
there may be a potential for undesirable incompatibilities
and a perceived increase in the risk of salt scaling
(Taylor et al. 2006). Judicious increases in dosage
can be accommodated with attention to detail in mix
proportioning and construction workmanship. Local
sources will often dictate the availability of acceptable
fly ash within a market.
Work is ongoing to find alternative methods to characterize
fly ash so that mixture performance can be
better predicted.
Slag cement, formerly known as ground granulated
blast furnace slag (GGBFS), is the material left after
extraction of iron from iron ore; see Figure 4.5. When
quenched from the molten state and ground to the
fineness of cement, it is an extremely effective SCM.
Slag cement is specified by ASTM C 989, and about 3
million tons are used in concrete in the United States
every year (SCA 2011). It is generally used in pavements
in dosages up to 50 percent but is limited by
concerns of early strength gain, especially when placed
during cooler ambient temperatures, and scaling
resistance. As with fly ash, usage tends to be regional
because of limitations on the cost effectiveness of
transporting it long distances.
3. Emerging Cementitious
Systems
Work is ongoing in many institutions looking at nonportland
cement based binders (Taylor 2010). Investigations
include the use of geopolymers (Van Dam
2010) and alkali-activated fly ash products as well as
materials fabricated using waste materials. These are
reported to carry significantly lower carbon and energy
burdens than portland cement while providing equivalent
or superior performance. Some new cements even
claim to consume CO 2 in manufacture (FHWA 2010).
Many systems have been patented, but they are generally
difficult to produce and work with. There are also
safety risks associated with some systems that require
the use of a highly alkaline activating solution. Some
systems may also require more processing, resulting in
increased energy consumption. Significant barriers to
the use of these materials are as follow:
• Portland cement is inexpensive and robust
• Practitioners are often resistant to change.
Future work on cementitious materials will likely
include finding alternative sources of raw materials
that will not involve the decomposition of carbonate
but rather use calcium-rich industrial byproducts, or
possibly shifting away from the use of calcium-based
cements entirely and perhaps using magnesium-silicate
raw materials.
The anatase form of titanium dioxide has been known
for decades to have the ability to keep surfaces clean.
A cement containing this compound is now available,
although it is more expensive than normal portland
cement. Titanium dioxide photocatalyic cements
reportedly can break down the harmful compounds of
nitrogen oxides (NOx) (Chen and Poon 2009). These
systems have been used in Europe, and trials sections
are being installed in the United States.
Figure 4.5 Petrographic optical micrograph of slag
cement particles (image courtesy of CTLGroup)
4. Aggregates
Aggregates comprise the bulk of the volume of a concrete
mixture. Important aggregate characteristics are
gradation, type/source, and durability.
30 Ch. 4. SUSTAINABLE CONCRETE PAVEMENT MATERIALS Sustainable Concrete Pavements A Manual of Practice

Gradation
Aggregates are often classified by particle size, being
normally defined as “coarse” and “fine” split at the
No. 4 (0.187 in. [4.75 mm]) nominal sieve opening.
This split is used to reduce the risk of segregation of
the material in stockpiles. Ideally the aggregates in a
concrete mixture should be composed of optimized,
well graded particle sizes representing the range of
sieve sizes (Taylor et al. 2006). This does not mean
that good concrete cannot be made with less than ideal
aggregate gradations, but the probability of success is
increased with improved aggregate systems.
If necessary, multiple aggregate stockpiles representing
different sized materials should be blended to create
the desired aggregate grading. This, and the use of as
large a nominal maximum aggregate size as practical
for a given situation, will allow the reduction of the
amount of cementitious materials required in a mixture
as shown in Figure 4.6, thus reducing costs and
environmental impact.
Aggregate Type
Natural
Natural aggregates, often referred to as pit-run gravels,
are extracted from river beds or pits with minimum
crushing or processing. They tend to be of a
mixed geological composition because they have been
transported some distance by natural forces. Energy
and CO 2 burdens associated with obtaining and
processing these materials are minimal because of the
limited amount of processing required. In some cases
washing is required to remove clayey dust, with the
attendant use of water which will have to be treated.
Sources of high-quality natural aggregates are being
depleted, leading to the need to consider whether the
current specification requirements (AASHTO M 6
and M 80/ASTM C 33) are overly restrictive or to find
methods to beneficiate unacceptable materials.
Natural aggregate particles tend to be rounded and
smooth from tumbling in rivers or glaciers, producing
good workability of the mixture but potentially reducing
flexural strength; see Figure 4.7.
Crushed
In locations where suitable natural aggregates are not
readily available, aggregate can be mined from bedrock
then crushed and sieved to suitable sizes; again, see
Figure 4.7. Generally the dust in these aggregates is
not clayey, and therefore higher quantities of material
passing the #200 sieve can be accommodated. Additional
energy consumption and emissions are associated
with mining and crushing activities to obtain
these materials. The selection of crushing equipment
can influence the shape of the aggregate particles, and
care should be taken to avoid systems that produce
Figure 4.6 Reduction of cementitious content with Figure 4.7 Rounded (left) and crushed natural
increasing coarse aggregate size (based on ACI aggregates (photo courtesy of Portland Cement
211) Association)
Sustainable Concrete Pavements A Manual of Practice Ch. 4. SUSTAINABLE CONCRETE PAVEMENT MATERIALS 31

narrow, flaky, or elongated particles, as these will
negatively impact workability and have a tendency to
fracture during processing.
The workability of mixtures made with crushed materials
is generally lower than in mixtures with rounded
aggregates, meaning that additional paste may be
required to achieve workability. On the other hand,
flexural strengths are normally higher.
Light-Weight Aggregates
Light-weight aggregate (LWA) is normally a manufactured
product, made by heating shale, clay, or slate in
a rotary kiln to about 2000°F; see Figure 4.8. The final
product is ceramic in nature and contains controlled
amounts of air bubbles, thus increasing aggregate
porosity and reducing density. Energy is required to
produce LWA. However, benefits have been reported
(in reduced cracking risk from internal curing) from
the use of a LWA as a portion of the fine aggregate
(Henkensiefken et al. 2009). Further, for structural
applications, the lighter weight will result in a reduction
of the structural members, meaning less concrete
will be required. LWA coarse aggregates are not commonly
used in pavements.
Recycled and Industrial Byproduct Materials
There is increased interest in recycling concrete and
other construction waste for use as aggregates in
paving concrete and supporting layers. This is beneficial
because it reduces the demand for virgin aggregates
and also reduces the need to place the waste
materials into landfills.
In pavements, the most common application for
recycled materials is in the subbase or base layers. This
can be achieved in-situ using mobile crushing equipment,
significantly reducing transportation costs and
environmental impact (Meijer 2008). If recycled materials
are used in concrete, the mixes have to be proportioned
and tested in the lab to ensure that setting times
and strengths are satisfactory. Consideration should
also be given to why the original pavement failed;
recycled concrete containing alkali-reactive aggregates
or aggregates prone to D-cracking may not be advisable
for use in paving concrete unless mitigated.
The most common industrial byproduct material used
as aggregate is air-cooled blast furnace slag (ACBFS)
which is produced from the iron blast furnace. This
material has been used in supporting layers and as
aggregate in paving concrete. Work currently being
conducted for the Federal Highway Administration
(FHWA) suggests that if ACBFS is used in paving concrete,
special design and construction considerations
must be followed to ensure acceptable performance
(Morian et al. 2011). Extreme caution must be exercised
if other sources of slag (e.g., steel furnace) are
being considered for use, as cases of extreme instability
and volume change have been reported in some
instances, which will lead to rapid pavement failure.
Other uses of recycled materials are discussed in
Chapter 8.
Durability
In general, aggregates have limited direct impact on
the durability of a mixture unless they are susceptible
to D-cracking or are reactive, which are serious issues,
or are easily polished.
Figure 4.8 Light-weight fine aggregate (image
courtesy of Buildex)
D-cracking is a problem where aggregates with relatively
high-porosity and low permeability tend to
absorb water that expands when it freezes, causing
the aggregate to fracture and the concrete to crack. It
is a regional problem, most common in the Midwest
from Kansas through southern Michigan and into
32 Ch. 4. SUSTAINABLE CONCRETE PAVEMENT MATERIALS
Sustainable Concrete Pavements A Manual of Practice

Ohio, in that aggregates prone to D-cracking tend to
come from a given geological form. Aggregates that
are prone to this should not be used if possible. If
they must be used, the susceptible aggregates should
be crushed to maximum size of 0.5 to 0.75 in. and
blended with larger, non-susceptible aggregates. This
will require that in some locations aggregates will need
to be imported, with the attendant fuel load. Research
is needed to find methods to prevent prone aggregates
from expanding or to find applications where they can
be safely used.
Alkali-silica reactivity (ASR) is a chemical reaction
between certain siliceous minerals within aggregate
that react with alkali hydroxides in the concrete pore
solution, forming a gel that expands when it imbibes
water causing the concrete to crack. Almost every state
in the United States has reactive aggregates. Work is
ongoing to develop rapid, reliable tests to assess reactivity
of aggregates and mixtures and to find ways to
prevent their expansion. Use of certain SCMs, particularly
Class F fly ash and slag cement, are known to be
effective at mitigating expansion and damage from the
use of susceptible aggregates. Lithium nitrite is also
known to be an effective additive. See AASHTO PP
65-10, Determining the Reactivity of Concrete Aggregates
and Selecting Appropriate Measures for Preventing Deleterious
Expansion in New Concrete Construction, for recommended
testing protocols and mitigation strategies.
Alkali-carbonate reactivity (ACR) is a rare deleterious
reaction between certain dolomitic limestone of a
very specific microstructure and hydroxyl ions in the
concrete pore solution. The reaction is not perfectly
understood but likely involves both the expansive
formation of brucite (magnesium hydroxide) and the
dissolution and swelling of clay phases within the
aggregate. Alkali-carbonate reactivity is very damaging,
and there is no effective mitigation strategy; thus,
susceptible aggregate must not be used. See AASHTO
PP 65-10, Determining the Reactivity of Concrete Aggregates
and Selecting Appropriate Measures for Preventing
Deleterious Expansion in New Concrete Construction, for
recommended testing protocols.
Polishing is the tendency of an aggregate at the pavement
surface to become smooth under the action of
traffic, leading to a reduction in skid resistance. Some
states resort to limiting the amount of calcareous materials
in their aggregates to limit this effect, although
many states must use these materials because of their
abundance and lower risk of alkali-silica reaction. In
such cases, surface texturing becomes increasingly
important to maintain skid resistance.
5. Water
The amount of mix water in paving concrete is primarily
governed by the w/cm ratio and paste requirement
of the aggregate system and the type and dosage of the
chemical admixtures in use. The presence of SCMs
will normally reduce the amount of water needed for
a given cementitious content. Therefore, choosing
a good aggregate system, reducing the cementitious
content (within limits), and using water-reducing
admixtures will all help to reduce the amount of
water required to achieve a given workability. There is
normally more water in a typical paving mixture than
is required to hydrate all the cement. Typically added
water accounts for about 6 percent of the mass of a
mixture.
The quality of the mix water is normally not much of a
concern. Water that is potable is considered acceptable
for use in concrete. Water contaminated by organics
and sugars will tend to delay setting and may reduce
early strengths. Grey water or water that has been recycled
at a batch plant may accumulate dissolved solids,
sulfates, and chlorides that may affect mixture performance
and durability. Therefore, wash water used to
clean tracks and equipment, as well as water recycled
from returned trucks, should be processed to remove
solids and organics before it is released to the environment
or before it is re-used in a batch plant. ASTM C
1602 provides some limitations on the quality of mix
water, particularly recycled water and wash water.
Two other significant uses of water at a construction
site are for achieving the appropriate moisture content
to facilitate densifying soil and unbound granular
materials and for dust control. The amounts of water
used should be balanced between the needs to achieve
engineering requirements and to minimize waste. Dust
control on unpaved surfaces can be enhanced by the
use of calcium chloride.
Sustainable Concrete Pavements A Manual of Practice
Ch. 4. SUSTAINABLE CONCRETE PAVEMENT MATERIALS 33

6. Admixtures
Chemical admixtures are a common constituent in
modern paving concrete, being added to modify one
or more of the fresh or hardened properties of the
concrete. Chemical admixtures are typically used in
pavement mixtures to entrain air, increase workability,
and/or control time of setting. Admixtures are used
in small dosages and usually comprise less than 0.2
percent by volume of concrete.
Common chemical admixtures are specified using
AASHTO M 154/ASTM C 260 and AASHTO M 194/
ASTM C 494. The basic ingredients used in waterreducing
and retarding admixtures are sugars and
lignosulfonates obtained from corn or wood. The most
common accelerating admixture is calcium chloride,
although non-chloride based accelerators are also
available. The primary materials used in modern
high-range water-reducing admixtures (HRWRA) are
polycarboxylate ethers and polyvinyl copolymers synthesized
from oil-based materials.
Water-reducing admixtures (WRAs) are primarily used
to reduce the amount of water required in a mixture to
achieve a given workability. For a mixture with a fixed
w/cm ratio, water reducers can be used to reduce the
amount of cementitious material required, leading to
significant savings in cost and environmental impact.
They also permit use of lower w/cm ratios in mixtures,
leading to improved durability and longevity.
the amount of steel used in continually reinforced
concrete pavements (CRCP) can be significant; therefore,
the designer must balance the environment and
cost impacts of including the steel with the improved
longevity of the pavement.
Dowel bars (smooth bars), or simply dowels, are
placed in concrete across transverse joints to provide
vertical support and to transfer loads across joints.
Dowel bars are typically used on heavy truck routes.
Dowel bars reduce the potential for faulting, pumping,
and corner breaks in jointed concrete pavements
(Smith et al. 1990, ACPA 1991).
Tiebars (deformed bars), or rebar, are placed across
longitudinal joints on centerlines or where slabs meet.
Tiebars prevent faulting and lateral movement of
the slabs and assist with load transfer between slabs.
Tiebars are also used to connect edge fixtures such as
curbs and gutters to the pavement.
Reinforcement may be used in concrete pavements to
improve the ability of concrete to carry tensile stresses
and to hold tightly together any random transverse
cracks that develop in the slab; see Figure 4.10. Generally,
cracking in jointed concrete pavements is controlled
by limiting the spacing between joints. When
the concrete slab is reinforced, joint spacing can be
Air-entraining admixtures (AEAs) are used to develop
a system of small air bubbles to increase the resistance
of critically saturated concrete to deicer salt scaling
and cyclic freezing and thawing, increasing longevity
of the pavement; see Figure 4.9.
As previously mentioned, lithium-based admixtures
can be used to mitigate alkali-silica reaction.
7. Reinforcement
Dowel bars, tiebars, and reinforcement may be used
in concrete pavements to help the concrete carry
tensile stresses and/or to transfer loads across joints.
The most common reinforcement material is steel,
and the energy requirement to process steel is high.
Dowels and tiebars are used in small quantities, but
Figure 4.9 Air-entrained concrete (image courtesy
of CTLGroup)
34 Ch. 4. SUSTAINABLE CONCRETE PAVEMENT MATERIALS Sustainable Concrete Pavements A Manual of Practice

increased. The most common reinforcement is embedded
steel placed either as welded wire fabric or as reinforcement
bars. Fiber-reinforcement can also be used.
Fibers are commonly composed of steel or polymers,
although various other materials (e.g., carbon, cellulose,
glass, and so on) have been used.
8. Proportioning
The aim of mixture proportioning is to find the
combinations of available and specified materials that
will ensure that a mixture is cost effective and meets
all performance requirements. In the case of sustainable
design, minimizing the pavement’s environmental
footprint (e.g., embodied energy and GHG emissions)
over the pavement life cycle must be one of the performance
requirements.
The freedom to vary mixture proportions depends on
the specification. There is a movement to write specifications
that are less “recipe” based and more focused
on the desired performance. This places decision making,
and risk, in the hands of the concrete provider
and paving contractor, with the attendant economic
and environmental impacts. Such a trend will mean
that everyone in the process has to be better educated
about the broad impacts of their decisions.
Ideally a concrete paving mixture will use an optimized
combined aggregate gradation that minimizes
voids and thus the paste requirement, resulting in
minimal cement and water required. Achieving this
should not be at the expense of significantly increased
processing or transportation impacts.
Aggregates should be resistant to the environment and
not prone to D-cracking, ASR, or ACR. Cementitious
content should be kept as low as possible without
compromising mixture performance, both in the fresh
and hardened state. The selection of the cementitious
system should be to maximize SCM contents while
preventing ASR, resisting freezing and thawing distress,
and meeting other specified requirements. The
quality of the paste, including the w/cm ratio and airvoid
system, should be selected based on the environment
to which the mixture will be exposed.
Guidelines for achieving these objectives are available
in Integrating Materials and Construction Practices for
Concrete Pavements (Taylor et al. 2006).
9. References
American Coal Ash Association (ACAA). 2009. Coal
Combustion Product Production and Use Survey Report.
(www.acaa-usa..org/associations/8003/files/2009_Production_and_Use_Survey_Revised_100511.pdf;
accessed Dec. 5, 2011)
Bhatty, J.I., J. Gajda, D. Broton, and F. Botha. 2006.
Coal-Prep Wastes in Cement Manufacturing–Commercialization
of Technology. ICCI Project Number: 04-1/4.1A­
2. Illinois Clean Coal Institute.
U.S. Environmental Protection Agency (EPA). 2010.
Inventory of U.S. Greenhouse Gas Emissions and Sinks:
1990–2008. Washington, D.C.: U.S. EPA. EPA
430-R-10-006.
Federal Highway Administration (FHWA). 2010.
Advanced High Performance Materials For Highway
Applications. FHWA-HIF-10-002. Washington, D.C.:
FHWA.
Figure 4.10 Reinforcing for CRCP (photo courtesy
of Mike Ayers,American Concrete Pavement
Association)
Hanle, L.J., K.K. Jayaraman, and J.S. Smith. ND. CO 2
Emissions Profile of the U.S. Cement Industry. Washington,
D.C.: U.S. EPA. (www.epa.gov/ttn/chief/conference/ei13/ghg/hanle.pdf;
accessed Dec. 5, 2011)
Sustainable Concrete Pavements A Manual of Practice Ch. 4. SUSTAINABLE CONCRETE PAVEMENT MATERIALS 35

Henkensiefken, R., D. Bentz, T. Nantung, and J. Weiss.
2009. “Volume change and cracking in internally
cured mixtures made with saturated lightweight aggregate
under sealed and unsealed conditions.” Cement &
Concrete Composites, 31.
Hooton, R.D., M. Nokken, and M.D.A. Thomas. 2007.
Portland Limestone Cements: State-of-the-Art Report and
Gap Analysis for CSA A 3000. SN3053. Cement Association
of Canada.
Kostmatka, S. H., and M.L. Wilson. 2011. Design
and Control of Concrete Mixtures, 15th Ed. PCA EB1.
Skokie, IL: Portland Cement Association.
Malhotra, V.M. 2000. “Role of Supplementary Cementing
Materials in Reducing Greenhouse Gas Emissions.”
In Concrete Technology for a Sustainable Development in
the 21st Century, Gjorv, O. E. and K. Sakai, Eds. London:
Taylor & Francis.
Meijer, J. 2008. “Environmental Benefits of Two-
Lift Pavement: A Quantitative Perspective Based on
Life Cycle Assessment.” Presentation made at 2008
National Two-Lift Paving Open House, Salina, KS.
(www.cptechcenter.org/projects/two-lift-paving/
documents/-Environmentalbenefits-JMeijer.pdf;
accessed Dec. 5, 2011)
Michigan Institute of Technology (MIT). 2010. Life
Cycle Assessment (LCA) of Highway Pavements: Interim
Report. Cambridge, MA: MIT, Concrete Sustainability
Hub. (http://web.mit.edu/cshub/news/pdf/PavementsLCAsummaryDec2010.pdf;
accessed Dec. 5, 2011)
MIT. ND. (Various news articles.) (http://web.mit.edu/
cshub/news/news.html; accessed Dec. 5. 2011)
Morian, D., T. Van Dam, K. Smith, and R. Perera.
2011. Use of Air-Cooled Blast Furnace Slag as Coarse
Aggregate in Concrete Pavements: A Guide to Best Practice.
Washington, D.C.: FHWA. In publication.
National Renewable Energy Laboratory (NREL). 2011.
U.S. Life-Cycle Inventory Database. (www.nrel.gov/lci/;
accessed Dec. 5, 2011)
Portland Cement Association (PCA). 2009. Report on
Sustainable Manufacturing. Skokie, IL: PCA. (www.
cement.org/smreport09/index.htm; accessed Dec. 5,
2011)
Slag Cement Association (SCA). 2011. (http://slagcement.org/;
accessed Jan. 2011)
Taylor, P. C. 2010. “New Technologies for Sustainable
Concrete.” In Proceedings-Concrete for a Sustainable
Environment. Johannesburg, SA: Concrete Society of
Southern Africa.
Taylor, P., S. Kosmatka, G. Voigt, et al. 2006. Integrating
Materials and Construction Practices for Concrete
Pavements: A State-of-the-Practice Manual. Ames, IA:
National Center for Concrete Pavement Technology,
Iowa State University. FHWA HIF-07-004. (www.
cptechcenter.org/publications/imcp/index.cfm;
accessed Dec. 5, 2011)
Tikalsky, P.J., V. Schaefer, K. Wang, B. Scheetz, T. Rupnow,
A. St. Clair, M. Siddiqi, and S. Marquez. 2007.
Development of Performance Properties of Ternary Mixtures:
Phase I Final Report. Ames, IA: National Concrete
Pavement Technology Center, Iowa State University.
Van Dam, T., and K. Smith. 2011. Blended and Performance
Cements. ACPT Tech Brief. Washington, D.C.:
FHWA. FHWA-HIF-XX-XXX. In Publication.
Van Dam, T., and P. Taylor. 2009. Building Sustainable
Pavements with Concrete. Ames, IA: National Concrete
Pavement Technology Center, Iowa State University.
(www.cproadmap.org/publications/sustainability_briefing.pdf;
accessed Dec. 5, 2011)
Van Dam, T., B. Smartz, and T. Laker. 2010. “Use of
Performance Cements (ASTM C 1157) in Colorado
and Utah: Laboratory Durability Testing and Case
Studies.” Presentation made at International Conference
on Sustainable Concrete Pavements, Sacramento,
CA.
Van Dam, T.J. 2010. Geopolymer Concrete. CPTP Tech
Brief. Washington, D.C.: FHWA, Concrete Pavement
Technology Program. FHWA-HIF-10-014.
World Business Council for Sustainable Development
(WBCSD). 2010. (www.wbcsd.org/cement; accessed
Dec. 5, 2011)
36 Ch. 4. SUSTAINABLE CONCRETE PAVEMENT MATERIALS Sustainable Concrete Pavements A Manual of Practice

Chapter 5
CONSTRUCTION
Gary Fick
Duration of the construction phase is relatively short
compared to the total life of a concrete pavement. One
might assume, therefore, that the potential for sustainability
improvements during the construction phase is
limited. In fact, the opposite is true: A large contributor
to a concrete pavement’s sustainability is its long
service life, which is directly related to initial construction
quality. Efforts to enhance sustainability through
optimized design and material selection can be negated
through improper construction processes and/or a lack
of quality control; see Figure 5.1.
After a brief overview of sustainability issues related to
concrete pavement construction, this chapter discusses
how these issues can be addressed during the various
phases of a traditional, slipform paving construction
project. The chapter ends with brief discussions of
other construction methods and their potential for
enhancing pavement sustainability.
Figure 5.1 Initial construction quality helps
realize the designed long-term performance
(image courtesy of Gary Fick,Trinity Construction
Management, Inc.)

1. Overview of Construction
Issues Related to Sustainability
In addition to implementing proper construction and
quality control processes that ensure a durable, long-life
pavement, maximizing pavement sustainability during
the construction phase involves addressing immediate
environmental and societal impacts of construction.
These include the following:
• Erosion and storm water runoff
• Emission of greenhouse gases and particulates
through equipment exhaust stacks
• Generation of airborne dust particulate from construction
processes
• Noise generated from construction processes
• Increased road user cost due to traffic delays caused
by construction
To address both the short- and long-term impacts of the
construction process on pavement sustainability, three
categories of activities should be emphasized:
• Reducing construction-related waste and disruption
to the surrounding area
• Optimizing equipment for maximum fuel efficiency to
minimize both consumption and exhaust emissions
• Constructing durable concrete pavements as indicated
by the following characteristics (specifications
will vary by agency):
a. Optimized paste content
b. Low permeability
c. Adequate entrained air
d. Strength and thickness as specified
e. Uniform mixture properties (within batch and
between batches)
In most cases, these issues are addressed as a matter of
practice, as contractors are concerned with maximizing
efficiency and minimizing costs. The rest of this chapter
outlines specific considerations related to these activities
in all the phases of construction. Table 5.1 summarizes
concrete pavement construction practices that can lead
to improved sustainability.
It should be noted that discharge of materials from a
roadway construction project is regulated by federal
law and enforced individually by each state. Regulations
and mitigation measures are ever changing and
apply equally to all types of roadway construction
projects. There are no specific measures for concrete
pavement projects that differ from other types of roadway
construction. Therefore, this facet of environmental
impact is not addressed specifically in this chapter.
Readers should fully inform themselves of the appropriate
statutory regulations regarding the discharge of
erodible materials and sediment from a project site.
2. Traditional Slipform Paving
Processes and Impacts on
Sustainability
In this section, sustainability-related factors and
suggestions are provided to manage the economic,
environmental, and social impacts of various slipform
pavement construction processes.
Establishing and Operating a Plant Site
Typically, for projects over 10,000 yd 3 a dedicated concrete
plant is mobilized. Doing so requires that a plant
site be selected and stripped of vegetation and topsoil.
The site may be chemically stabilized and/or plated
with granular material to minimize pumping soil into
the aggregate stockpiles and to provide a more weatherproof
hauling surface for trucks.
Managing Economic Impacts
• First, locate the plant site to minimize the average
haul distance for the concrete.
• Second, locate the site to minimize the haul distance
from the supplier’s point of distribution for
aggregate material, which comprises the largest
volume of the concrete mixture.
Managing Environmental Impacts
• Storm water runoff and washout water/sediment
should be contained and/or filtered to prevent
contamination of local waterways (local statutory
requirements apply).
38 Ch. 5. CONSTRUCTION Sustainable Concrete Pavements A Manual of Practice

• A combination of granular materials, such as
recycled pavement materials, and water sprinkling
should be used for dust control.
• Tracking mud onto public roadways should be
controlled through the use of a stabilized construction
entrance. Portable wheel wash systems may be
necessary and/or required in some jurisdictions.
• Plant sites should be re-vegetated as soon as practical
after construction to prevent detrimental runoff.
• Avoid extended idling of diesel-powered equipment
to reduce greenhouse gas emissions.
Managing Social Impacts
• Public rights of way owned by the agency should
be made available to the contractor for use as plant
sites and borrow sources whenever possible to
minimize impacts on the public.
• The plant site should be located far enough from
residential areas that noise and dust can be mitigated
to a level that is not objectionable.
• Utilize brownfield sites whenever available and
economically feasible.
Stockpiling Aggregate
Aggregates are typically stockpiled using front-end
loaders (Figure 5.2) or radial stackers (Figure 5.3).
Either method is acceptable from a quality standpoint
as long as segregation is prevented. Segregated
aggregate can lead to non-uniformity during concrete
production, which will reduce long-term performance.
Managing Economic Impacts
• Radial stackers typically conserve energy when
connected to an existing power grid, due to more
Table 5.1 Summary of Concrete Pavement Construction Practices That Enhance Pavement Sustainability
Construction Practice
Providing a uniform concrete mixture that meets specifications
Placing dowels, tiebars, and reinforcing in the proper location
Using proper finishing techniques
Constructing smooth pavements
Ensuring timely and effective curing of the concrete pavement
Using alternative fuels
Reducing idling of diesel engines
Using equipment that meets or exceeds EPA emission requirements
Allocating equipment resources wisely by matching the quantity and
size of equipment to project needs
Implementing appropriate erosion control measures
Containing washout sediment
Optimizing plant site location with respect to the average haul
distance for concrete and delivery of raw materials
Properly constructing and maintaining haul routes
Water sprinkling of haul routes and plant sites for dust control
Recycling washout water
Stabilizing construction entrances where construction traffic enters
public roadways
Using public rights of way for plant sites, staging areas, and borrow
sources
Mitigating construction noise from exhaust stacks, banging tailgates,
plant site operations, and sawing
Considering traffic delays when planning project staging and logistics
Implementing accelerated construction methods that result in reduced
construction durations and earlier opening of facilities
Constructing subgrade and subbase(s) to tighter tolerances
Texturing
Sustainability Benefits
• Enhanced long-term pavement performance
• Smoother pavements, which result in improved
fuel efficiency and reduced vehicle maintenance
costs for the traveling public
• Reduced greenhouse gas and particulate emissions
• Utilization of fuel generated from renewable
sources
Improved energy efficiency
Preserved water quality in surrounding bodies of
water
Reduced fuel consumption
Control of objectionable airborne particulates
Conservation of water
Mitigation of sediment runoff
Minimized environmental impacts on private
property
Reduced negative impacts on the neighboring
communities
Reduced road user costs caused by delays
Reduced concrete waste and enhanced probability
of achieving smooth pavement
Enhanced safety through proper friction
characteristics and reduced tire-pavement noise
Sustainable Concrete Pavements A Manual of Practice Ch. 5. CONSTRUCTION 39

efficient burning of fuel used in commercial generation
of electricity.
• Front-end loaders may be the preferred option when
radial stackers are powered by an on-site generator that
is not being utilized for other plant site activities.
Managing Environmental Impacts
• All equipment (generators, front-end loaders) should
conform to EPA requirements, and the use of alternative
fuels should be considered whenever economically
feasible, to reduce GHG and particulate emissions
from diesel exhaust.
• Radial stackers connected to an existing power grid
likely result in fewer emissions due to more efficient
burning of fuel used in commercial generation of
electricity.
Managing Societal Impacts
• Noise and dust from the plant site should be mitigated
through proper site selection and sprinkling.
Establishing and Maintaining Haul Routes
In most cases, haul routes are constrained by construction
staging and the maintenance of traffic. The primary
sustainability-related issue that should be considered is
preparing and maintaining the haul route in a smooth
and stable condition. Fuel efficiency of the haul units will
degrade on soft/yielding haul routes. Rough haul routes
will lead to an increase in repairs and maintenance to the
haul units. Extremely rough haul routes can cause the
mixture to segregate when non-agitating trucks are used.
Managing Economic Impacts
• Fuel efficiency is affected by haul route stability. Temporary
haul routes may be stabilized with recycled materials
that can be re-used in later phases of the project.
• Haul routes should be maintained in a condition that
will reduce the occurrence of unnecessary vehicle
repairs and maintenance.
• Maintaining the haul routes in good condition will
also reduce the average cycle time for concrete delivery,
thus requiring fewer trucks and reducing the
quantity of fuel used per cubic yard of concrete.
Managing Environmental Impacts
• Dust should be controlled by sprinkling the haul
route with water.
• Tracking mud from the haul route on to public
roadways should be minimized by constructing
stabilized construction entrances.
Managing Societal Impacts
• Locations where haul units exit and enter public
roadways should be monitored to reduce traffic
delays experienced by the public.
• Excessive noise generated by haul units (exhaust
stack, banging tailgates, etc.) should be remedied.
Concrete Production
Recommendations regarding materials and proportioning
of concrete mixtures from a sustainable perspective
are addressed in Chapter 4. Once a mixture
has been optimized with regard to sustainability, the
concrete production process should be monitored
and adjusted as needed to achieve the desired results.
Figure 5.2 Front-end loader used for stockpiling
aggregate (photo courtesy of Gary Fick,Trinity
Construction Management, Inc.)
Figure 5.3 Stockpiling aggregate with a radial
stacker (photo courtesy of Gary Fick,Trinity
Construction Management, Inc.)
40 Ch. 5. CONSTRUCTION Sustainable Concrete Pavements A Manual of Practice

Concrete used for pavement is produced at either a
central mix plant (Figure 5.4) or a dry batch plant utilizing
transit mix trucks (Figure 5.5). Regardless of the
equipment used, it is imperative that the plant produce
a concrete mixture that meets or exceeds specification
requirements, is uniform within each batch, and is also
uniform from batch to batch. Non-uniform concrete
leads to non-uniform performance, which in turn
results in premature failure with related maintenance
and rehabilitation costs.
Non-uniformity of the concrete mixture can also lead
to wasted materials, because the concrete producer
is forced to use more cementitious material to consistently
meet specifications. A preferred approach is
to implement quality assurance procedures that will
improve uniformity and lead to the most efficient use
of materials.
Most concrete plants utilized for concrete paving projects
are equipped with automated batching controls.
While this certainly improves productivity, it is no
Figure 5.4 Central mix concrete plant (photo
courtesy of Jim Grove, FHWA)
guarantee that quality is improved. Attention to details
is required.
In particular, the moisture content of the aggregates
should be tested frequently and the mixture proportions
adjusted according to the moisture condition of
the aggregates being incorporated into the concrete.
Thorough mixing is also necessary. There are many
differing specifications regarding mixing time. Mixing
for the minimum specified time may or may not
produce uniform concrete that meets specification.
Each concrete plant and each mixture is unique; mixer
uniformity tests (ASTM C 94) should be utilized to
determine the minimum acceptable mixing time to
produce uniform concrete.
Water is a natural resource that should be conserved.
However, conserving water should not come at the
expense of dust control or concrete quality (e.g., washing
out trucks and cleaning the paver properly). Washout
water generated at the concrete plant site should
be recycled whenever possible.
The decision about source of water to use on a concrete
paving project should be based on three criteria:
First, concrete quality. Mixing water should be free of
organics that can degrade quality. Second, the environment.
The overall environmental impact of various
source options should be considered. Because most
potable water sources have been treated in some manner,
there is an associated energy expenditure that is
not necessarily needed for the production of concrete.
However, using sources of untreated water (wells,
ponds, and streams) may have an adverse impact on
the environment. Some environmental compromise
is associated with the choice of a water source. Third,
economic factors. Costs must be factored into the decision
process for choosing a source of water.
Managing Economic Impacts
• Energy efficiency is improved by matching plant
production capabilities to the paving operation.
Figure 5.5 Ready mix concrete plant (photo
courtesy of Jim Grove, FHWA)
• The production of uniform, high-quality concrete
leads to concrete pavements that perform as
expected or better than expected; thus, the lifecycle
costs of these pavements are lower than for
pavements that have premature failures due to
quality deficiencies, non-uniformity, or both.
Sustainable Concrete Pavements A Manual of Practice
Ch. 5. CONSTRUCTION 41

• Quality assurance procedures aimed at improving the
uniformity of the concrete reduces cost through the
efficient use of material resources.
Managing Environmental Impacts
• Dust collectors on concrete plants should be in
proper working order.
• Dust should be controlled by sprinkling the haul
route with water.
• Control harmful runoff from washout pits.
• Recycle washout water whenever possible.
• Dust generated by plant site traffic should be controlled
by sprinkling with water.
• Quality assurance procedures aimed at improving the
uniformity of the concrete ensure the efficient use of
material resources.
Managing Societal Impacts
Noise sources at the concrete plant that are a nuisance to
neighboring businesses or residences should be mitigated.
Transporting Concrete
Various types of hauling equipment are available for
transporting concrete for a paving project. These range
from transit mix trucks (Figure 5.6) to tractor-trailer rigs
(Figure 5.7). From a sustainability perspective, efficiency
should be maximized by matching the type, size, and
number of haul units to project constraints (production
rate, haul route conditions, maneuverability, etc.).
Haul units must be washed out frequently enough to
prevent the build-up of hardened concrete which may
eventually break free and be incorporated in the pavement,
causing a future pavement failure. (See the discussion
of water use in the immediately preceding section.)
Washout pits (Figure 5.8) should be designed to control
harmful runoff.
Figure 5.6 Transit mix concrete truck (photo
courtesy of Gary Fick,Trinity Construction
Management, Inc.)
Figure 5.7 Tractor trailer concrete hauling unit
(photo courtesy of Gary Fick,Trinity Construction
Management, Inc.)
Managing Economic Impacts
Haul efficiency should be maximized by matching
the type, size, and number of haul units to the project
conditions.
Managing Environmental Impacts
• All equipment should conform to EPA requirements,
and the use of alternative fuels should be considered
whenever economically feasible to minimize emission
of GHGs and particulate through diesel exhaust.
Figure 5.8 Washout pit used to clean concrete
trucks (photo courtesy of Gary Fick,Trinity
Construction Management, Inc.)
42 Ch. 5. CONSTRUCTION Sustainable Concrete Pavements A Manual of Practice

Managing Societal Impacts
• Excessive noise generated by haul units (exhaust
stack, banging tailgates, etc.) should be remedied.
• Locations where haul units enter and exit public
roadways should be monitored to reduce traffic
delays experienced by the public.
Concrete Placement and Finishing
Placing and finishing concrete pavement is a complex
process that involves the use of sophisticated equipment
in conjunction with the skilled craftsmanship
of crew members. By the time the concrete mixture is
deposited ahead of the paver, there is nothing that the
equipment and crew can do to improve the material
properties; these properties are strictly a function of
the raw materials, mixture proportions, and mixing
process. However, there are many ways that placement
and finishing techniques can negatively influence what may
be an otherwise acceptable concrete mixture. From a sustainability
perspective, it is imperative that the equipment
and crew place and finish the concrete pavement
in a manner that will maximize the performance
capabilities of the concrete mixture.
The following items summarize the placing and finishing
processes that are most critical to achieving the
long-term pavement performance that is integral to
concrete pavement sustainability. Detailed guidance
regarding these practices can be found in the Integrated
Materials and Construction Practices for Concrete Pavement
(Taylor et al. 2006) and Concrete Pavement Field
Reference: Pre-Paving (APWA 2010).
• Embedded steel must be properly placed.
a. Dowel baskets should be placed in the proper
location, anchored firmly, and positively marked
to ensure that saw cuts for contraction joints are
made at the proper location.
b. Inserted dowels should be monitored for movement
and positively marked to ensure that saw
cuts for contraction joints are made at the proper
location.
c. Tiebars should be placed at the proper depth
and spacing.
d. Continuous reinforcing bars should be spaced
according to specifications and supported in a
manner that will prevent displacement during
the paving process.
• Concrete should be well consolidated but not segregated.
Vibrator frequency should be monitored and
adjusted to variations in the concrete mixture and
the paver speed. Cores of the pavement should be
taken as soon as possible and visually inspected to
verify that consolidation efforts are adequate and
not detrimental.
• Proper hand finishing techniques should be consistently
implemented.
a. Except in rare and isolated conditions, water
should not be used as a finishing aid. The practice
of adding water to the surface of the pavement
can result in a weakened layer of non-durable
paste at the pavement’s surface.
b. Care must be take not to over-finish the surface.
Over-finishing results in a paste-rich, high-permeability
surface layer, which is susceptible to
shrinkage cracking and surface scaling.
• Acceptable pavement smoothness characteristics
must be achieved by following best practices for
placing and finishing.
Managing Economic Impacts
• Paving equipment should be matched to project
conditions.
• Subgrade and subbase(s) should be placed to thickness
and smoothness tolerances that will minimize
waste and meet thickness tolerance specifications
for the concrete pavement.
Managing Environmental Impacts
• Smooth pavements improve fuel efficiency.
• Dust should be controlled by sprinkling with water.
Managing Societal Impacts
• Construction noise should be mitigated to reduce
impacts on surrounding areas.
• Dust should be controlled by sprinkling with water.
• Smooth pavements reduce wear and tear on vehicles.
Sustainable Concrete Pavements A Manual of Practice Ch. 5. CONSTRUCTION 43

Surface Texturing
Concrete pavement surface textures provide the friction
needed for safe roadways. Surface textures have
also been shown to be the primary contributor to
pavement-tire noise. There are three basic types of
concrete pavement surface textures, as shown in
Table 5.2.
Guidance regarding improved procedures for concrete
texturing that contribute to constructing quieter pavements
can be found in How to Reduce Tire-Pavement
Noise: Interim Better Practices for Constructing and
Texturing Concrete Pavement Surfaces (Rasmussen et al.
2008).
Table 5.2 Concrete Pavement Surface Texture Types
Variations
/ Uses
Tined
(Figure 5.9)
Texture Types
Drag
(Figure 5.10)
Diamond
Ground
(Figure 5.11)
• Transverse, • Burlap • New
uniform spacing
• Artificial
surface
• Transverse, turf • Restored
random spacing
• Broom
surface
• Longitudinal,
uniform spacing
Managing Economic Impacts
Diamond ground textures generally cost more than
tined or drag textures.
Managing Environmental Impacts
Slurry from diamond ground textures should be collected
and disposed of properly.
Figure 5.9 Longitudinal tining (photo courtesy of
Gary Fick,Trinity Construction Management, Inc.)
Managing Societal Impacts
• Adequate friction characteristics must be provided
for safe roadways.
• Studies have shown that tire-pavement noise is
attributable to positive texture on concrete pavements.
Quieter pavements have textures with fewer
positive projections in the surface.
Curing Concrete
Perhaps one of the most overlooked parts of the concrete
paving process, curing has a significant impact
on concrete pavement durability and thus on sustainability.
Curing must be executed properly to prevent
excessive moisture loss and thus to ensure that sufficient
water is available in the concrete to completely
hydrate the cementitious materials and to prevent
shrinkage cracking and excessive warping.
In general, white pigmented curing compound should
be applied before any surface evaporation occurs. All
exposed surfaces of the concrete pavement should
be completely covered (the pavement surface should
be uniformly white). Precautions should be taken to
Figure 5.10 Artificial turf drag texture (photo
courtesy of Gary Fick,Trinity Construction
Management, Inc.)
Figure 5.11 Diamond-ground texture (Rasmussen et
al. 2008)
44 Ch. 5. CONSTRUCTION Sustainable Concrete Pavements A Manual of Practice

insulate the concrete during cold weather curing to
prevent the pavement from freezing before gaining sufficient
strength.
Managing Economic Impacts
Although curing compounds and the curing process
itself constitute one of the least expensive components
of the concrete paving process, premature failures associated
with inadequate curing result in unnecessary
future maintenance and rehabilitation expenditures.
Managing Environmental Impacts
• Some curing compounds may contain materials that
could be hazardous to the environment. If spills
occur, they should be contained and mitigated in
accordance with local regulations.
• Use of environmentally benign curing compounds
should be considered when allowed by specification.
Managing Societal Impacts
Prevention of premature pavement distresses and
related repair activities through the proper application
of curing compound and techniques reduces work
zone-related traffic delays.
Sawing and Sealing Joints
Sawed joints are necessary for non-reinforced pavements
to prevent uncontrolled cracking. Practices for
sawing and sealing joints vary across the United States.
The most common options for green sawing concrete
pavement are wet sawing with diamond blades (saw
cut depth = T/4 or T/3) and early entry sawing using a
dry diamond blade (saw cut depth = 1 in. to 3 in.).
Dimension sawing (joint widening) is necessary for
certain joint sealants that require a specific joint shape
for proper performance. This is most commonly performed
by wet sawing with stacked diamond blades
that create a joint reservoir from 3 ⁄8 in. to ½ in. wide
and 1 in. to 1½ in. deep.
Common joint sealant materials used for concrete paving
include bituminous (hot poured or cold poured),
silicone (tooled or self-leveling), and pre-formed compression
seals.
Managing Economic Impacts
• The cost and performance of joint sealants varies
widely. When specifying a joint sealant, performance
expectations should be balanced by costbenefit
analyses.
• Some states choose to leave joints unsealed. This
decision should be based on actual performance
studies that are applicable to the intended climate,
subbase design, and pavement use conditions.
Managing Environmental Impacts
• Slurry from wet sawing joints should not be allowed
to drain unfiltered into adjacent waterways.
• Some joint sealants may contain materials that are
hazardous to the environment and/or crew; manufacturers’
recommendations should be followed.
Managing Societal Impacts
• Measures should be taken to prevent the dust generated
by dry sawing joints from obstructing the visibility
of adjacent traffic.
• Tire-pavement noise associated with wide joints
(>½ in.) may be objectionable.
3. New Developments in Concrete
Pavement That Could
Improve Sustainability
Two Lift Concrete Pavements
As discussed in Chapter 3, two-lift paving is a technique
that is commonly used in Europe. The construction
process involves placing two lifts of concrete pavement,
with the top lift placed on the bottom lift while it
is still wet (Figures 5.12 and 5.13). Typically the bottom
lift is approximately 80 percent of the thickness and
the top lift is approximately 20 percent. Constructing a
concrete pavement in this manner allows for the use of
different mixture designs for the bottom lift and top lift.
Two-lift pavements can be constructed with conventional
paving equipment, although an additional belt
placer/spreader and an additional paver is required. It
is possible to offset these additional labor and equipment
costs by economizing the mixture design used for
the lower lift.
Sustainable Concrete Pavements A Manual of Practice Ch. 5. CONSTRUCTION 45

Two-lift pavements offer opportunities to improve the
sustainability of concrete pavements in the following
ways:
• Utilization of recycled pavement materials in the
lower lift
• Increased use of supplementary cementitious materials
in the lower lift
• Long-term performance enhancements associated
with an ultra-durable wearing surface
Roller-Compacted Concrete
Roller-compacted concrete (RCC) is constructed using
equipment similar to that used in the asphalt pavement
construction industry (Figure 5.14). The mixture is
placed with a heavy-duty paver and compacted with
a vibratory steel wheel and pneumatic rollers. RCC
mixtures utilize a greater amount of fine aggregate
particles and reduced cementitious and water contents
(Harrington et al. 2010). RCC contains no reinforcing
steel, reducing both the economic and environmental
impacts from the use of steel reinforcement. In certain
geographic areas that have an abundance of natural
sands and a shortage of quality coarse aggregates,
higher aggregate content makes RCC a sustainable
solution for low-speed applications (industrial lots,
streets, and local roads). RCC can also be opened to
light traffic earlier than conventional concrete pavement,
resulting in less disruption to the traveling public.
4. References
American Concrete Pavement Association (ACPA).
2008. Concrete Pavement Field Reference: Pre-Paving.
Report EB237P. Chicago, IL: ACPA.
Cable, J. 2004. Two Lift PCC Pavements to Meet Public
Needs. www.cptechcenter.org/projects/two-lift-paving/
cable-062707.pdf; accessed Dec. 5, 2011)
Harrington, D., F. Abdo, W. Adaska, and C. Hazaree.
2010. Guide for Roller-Compacted Concrete Pavements.
SN298. Ames, IA: National Concrete Pavement Technology
Center, Iowa State University.
Rasmussen, R.O., S.I. Garber, G.J. Fick, T.R. Ferragut,
and P.D. Wiegand. 2008. How to Reduce Tire-Pavement
Noise: Interim Best Practices for Constructing and Texturing
Concrete Pavement Surfaces. TPF-5(139). Ames, IA:
National Concrete Pavement Technology Center, Iowa
State University.
Figure 5.12 Top lift being placed on the bottom lift
(photo courtesy of Gary Fick,Trinity Construction
Management, Inc.)
Taylor, P., S. Kosmatka, G. Voigt, et al. 2006. Integrating
Materials and Construction Practices for Concrete
Pavements: A State-of-the-Practice Manual. FHWA
HIF-07-004. Ames, IA: National Center for Concrete
Pavement Technology, Iowa State University.
Figure 5.13 Two-lift paving on I-70 in Kansas
(photo courtesy of Gary Fick,Trinity Construction
Management, Inc.)
Figure 5.14 RCC placement (Harrington et al. 2010)
46 Ch. 5. CONSTRUCTION
Sustainable Concrete Pavements A Manual of Practice

Chapter 6
IMPACT OF THE USE PHASE
Martha VanGeem
Emily Lorenz
Tom Van Dam
As discussed in previous chapters, to obtain a full
measure of the environmental impact of a concrete
pavement, all phases of the pavement’s life cycle must
be considered. Although considerable attention has
been paid to the material acquisition and construction
phases, and to a lesser degree the end-of-life
phase, until recently little attention has been paid to
the impact of pavement type during the use phase.
Yet it is recognized that the use phase, particularly the
traffic using the facility, often has the largest impact on
the environment (Wathne 2010). As a result, increasing
emphasis is being placed on whether differences
resulting from pavement type may have a significant
effect on environmental impact over the life cycle, considering
such factors as vehicle fuel efficiency as well
as how the pavement interacts with the environment
while in service (Wathne 2010, Santero et al. 2011a).
This chapter briefly considers both aspects. Trafficrelated
factors such as vehicle rolling resistance, which
is influenced by pavement roughness and stiffness,
are discussed, as is pavement-environment interaction
including carbonation, lighting requirements, albedo,
and leachate. The latter are discussed in greater detail
in Chapter 9, as they are primarily a consideration in
urban environments.

1. Vehicle Fuel Consumption
Unlike buildings that have electricity and other
energy-related metrics directly attributed to their
use, the energy and associated environmental impact
attributed to the use of pavements are more difficult
to account. Although some of the energy used in the
operation of a pavement may be directly accounted
for (e.g., energy to power artificial lighting), the biggest
source of energy consumed during the use phase
is overwhelmingly the fuel consumption of vehicles
using the roadway. The consumption of fossil fuels has
the greatest environmental impact during the pavement
life cycle, due in part to the emission of GHGs,
but also many other environmentally harmful impacts
as shown in Figure 6.1.
Vehicle fuel consumption depends on many things
such as wind resistance, vehicle type and load, tire
type and pressure, vehicle speed and acceleration, and
the interaction between the vehicle and the pavement
surface, which includes pavement roughness (often
measured using the international roughness index or
IRI), surface texture, and stiffness, among other factors.
Many of these factors are the same regardless of
pavement type. Pavement roughness, surface texture,
and stiffness, however, are inherent features of the
pavement and thus can be controlled by the managing
agency, which has the ability to design, construct,
Figure 6.1 Ecoprofile of different life-cycle phases
from a typical road (Wathne 2010 based on EAPA
2004)
and maintain a pavement surface that will minimize
the economic and environmental impact of vehicle
operation.
The rolling resistance, which is the vehicle energy loss
associated with pavement-vehicle interaction, has to be
minimized for agencies to improve the fuel efficiency
of vehicles operating on their pavements (Santero et
al. 2011b). One of the biggest factors contributing
to rolling resistance is road roughness, as it results in
an excitation of the suspension systems in vehicles,
consuming energy that is responsible for significant
increases in fuel consumption (AASHTO 2009). This
has been a key input into the World Bank’s pavement
design model for decades (Chesher and Harrison
1987, Bennett and Greenwood 2003), and recent
studies have confirmed the validity of this conclusion
(Zabaar 2010). Specifically, it was found that regardless
of pavement or vehicle type, increasing pavement
roughness results in significantly higher fuel consumption
regardless of vehicle speed. This clearly demonstrates
the benefit of constructing smooth pavements
and keeping them smooth over their service life.
Further, increasing pavement texture (as measured
by the sand patch test) results in significant increases
in fuel consumption at lower vehicle speeds (Zaabar
2010). Sandberg (1990) had previously observed this
trend, finding that at higher speeds, rolling resistance
is less dependent on pavement surface texture because
vehicle fuel consumption is more heavily influenced
by air resistance.
These conclusions, which are consistent with previous
work conducted on vehicle operating costs, support
the need to construct smooth, safe, and quiet concrete
pavements and employ maintenance and preservation
strategies over the service life that will keep them
smooth, safe, and quiet. This enhances fuel efficiency
and reduces environmental impact; it will also reduce
the social cost of pavements by reducing crashes
(Tighe et al. 2000). As is described in Chapter 7, the
timely application of preventive maintenance treatments,
including the use of diamond surface grinding,
is a key strategy to keep good pavements in good
condition, enhancing sustainability over the life cycle.
In addition to pavement roughness and texture,
a number of field studies have been performed to
48 Ch. 6. IMPACT OF THE USE PHASE
Sustainable Concrete Pavements A Manual of Practice

determine if rolling resistance is affected by pavement
properties (Zaniewski et al. 1982, De Graaff 1999,
NPC 2002, Taylor and Patten 2006, Ardekani and
Sumitsawan 2010, Zaabar and Chatti 2011). Higher
pavement deflections may result in additional fuel
consumption as a vehicle moves along the pavement
surface (Akbarian 2011).
It is clear from past studies that no overwhelming
consensus has emerged from various field studies conducted
to determine whether pavement type impacts
fuel consumption, although it appears that pavement
type can make a difference, with slightly better fuel
efficiency observed for vehicles operating on concrete
pavements (Santero et al. 2011c). From this review, it
is clear that the study of fuel consumption is complicated
by many, many factors, and those field studies
that have taken this into account have found that pavement
type effects are most prevalent for heavier, slowmoving
vehicles during warm weather. As an example,
Zaabar and Chatti (2011) reported that pavement type
has a statistically significant impact on fuel efficiency
for light (loaded) trucks and heavy trucks moving at
low speeds (35 mph) under summer conditions, with
increased fuel consumption occurring on asphalt-surfaced
pavements. The results were statistically insignificant
at higher speeds for all vehicles, and for passenger
cars, vans, and SUVs under all conditions. It is noted
that data were not available for heavy trucks under
winter conditions.
These results make sense from an intuitive perspective
since a viscoelastic material such as asphalt will
stiffen as it cools and/or is subjected to a higher rate
of loading. As the surface stiffens, deflection decreases
and rolling resistance is reduced. Work conducted at
the Massachusetts Institute of Technology resulted in
a first-order mechanistic model to simulate the effect
of pavement stiffness on rolling resistance and to
accurately calculate the rate of fuel consumption for
different vehicle types for pavements of various stiffness
(Akbarian 2011). Preliminary results suggest that
pavement stiffness does make a small but significant
difference, with lower fuel consumption incurred
for all vehicle types operating on stiffer pavements.
The continued development of this type of model is
justified, as the volume of traffic over the life of many
pavements is so great that even a difference in fuel
consumption of only 1 or 2 percent can have a huge
economic and environmental impact over the design
life and should be incorporated into a life-cycle assessment
model as discussed in Chapter 8.
In summary, it is clear that vehicular operations are
responsible for most of the energy consumed and
emissions generated over a pavement’s life cycle.
Although many factors contributing to fuel consumption
are not related to the interaction between the tire
and pavement, the pavement roughness, texture, and
stiffness contribute to the rolling resistance. A concrete
pavement that is constructed and maintained in
a smooth condition will thus reduce rolling resistance
and increase fuel efficiency of vehicles operating on
it, thus reducing energy use and emissions. Further,
the inherent stiffness of concrete appears to result
in reduced fuel consumption, especially for heavy
vehicles operating at slow speeds during the warmer
months of the year. Mechanistic models are under
development that will properly consider vehicular rolling
resistance and its impact on fuel consumption for
use in life-cycle assessment.
2. Other Environmental Impacts
During Use
In addition to environmental impact incurred due to
vehicular use, other environmental factors warrant
consideration, including solar reflectance, lighting,
carbonation, run-off, and traffic delays. Santero et
al. (2011a) note that these factors are the least consistently
considered in the environmental life-cycle
assessment of pavements, yet in combination they can
have a significant environmental impact. Most of these
factors are addressed in greater detail in other chapters,
but they are mentioned here since they affect a
pavement in service.
Solar Reflectance
Solar reflectance (or albedo) is a surface property of a
material. Solar reflectance values range from zero to
1.0, with a zero value indicating a perfectly non-reflective
material and a 1.0 value representing a material
that is 100 percent reflective. Light-colored materials
have higher solar reflectance values than dark-colored
materials. Although color plays a role in a material’s
Sustainable Concrete Pavements A Manual of Practice
Ch. 6. IMPACT OF THE USE PHASE 49

solar reflectance, color alone is not the only indicator
of solar reflectance.
Solar reflectance has the greatest importance in urban
areas as it is known to contribute to the formation
of urban heat islands. A heat island is a local area of
elevated temperature located in a region of cooler temperatures.
Heat islands usually occur in urban areas
as illustrated in Figure 6.2; hence, they are sometimes
called urban heat islands. Urban heat islands are
formed due to the warming of exposed urban surfaces
such as roofs and pavements (EPA 2009). Urban heat
islands contribute to lower air and water quality and
greater energy demands, especially in the summer.
In places that are already burdened with high temperatures,
the heat-island effect can make cities warmer,
more uncomfortable, and occasionally more life-threatening
(FEMA 2007). Temperatures greater than 75˚F
increase the probability of formation of ground-level
ozone (commonly called smog), which exacerbates
respiratory conditions such as asthma. Higher temperatures
also lead to greater reliance on air conditioning,
which leads to more energy use and associated
emissions.
Due to its naturally light color, concrete is an excellent
choice for paving material in an urban environment.
This is illustrated in Figure 6.3, which shows the
impact of pavement albedo on surface temperature,
with darker surfaces having much higher temperatures.
Further, reflectance can be enhanced by the use
of some SCMs, such as light-colored slag cement and/
or fly ash. Highly reflective pavement surfaces can be
created using white titanium dioxide photocatalytic
cement or coatings, further mitigating the urban heat
island effect. Titanium dioxide photocatalyic coatings
have the added benefit of breaking down the harmful
compounds of nitrogen oxides (NOx) (Chen and Poon
2009). And, because of evaporative cooling, the use
of a light-colored pervious concrete pavement can be
extremely effective in addressing the urban heat island
while also addressing surface run-off. Further discussion
on this topic can be found in Chapter 9.
Further, the use of reflective surfaces, including the
use of reflective pavements and roofs in both urban
and rural areas, is being advocated by a group of
researchers at Lawrence Berkeley National Laboratory.
This is not being recommended for mitigation of
the urban heat island effect alone, but as a strategy to
combat global warming through radiative forcing of
the sun’s energy back into space (Akbari and Menon
2008). The basic theory is that when the sun’s energy
is reflected back into space, it is not being absorbed
into the earth’s surface and thus cannot contribute
to warming of the planet. Research continues into
the impact of radiative forcing on mitigating global
warming, but findings to date indicate that this could
be an enormously important factor in reducing global
temperatures in the future.
Lighting
Concrete’s higher (brighter) reflectance can also
lower infrastructure and ongoing lighting costs, while
boosting safety for vehicles and pedestrians. Concrete
Figure 6.2 Heat islands for various areas of
development (EPA 2003)
Figure 6.3 Effect of pavement type and albedo on
pavement surface temperature (Kaloush 2010)
50 Ch. 6. IMPACT OF THE USE PHASE Sustainable Concrete Pavements A Manual of Practice

pavements require fewer lighting fixtures than other
surfaces and less energy is required to achieve the
same degree of lighting (Gajda and VanGeem 2001).
Improved illumination leads to increased visibility,
which is an important safety consideration. This is also
discussed in more detail in Chapter 9.
Carbonation
Carbonation is a normal phenomenon that occurs
between hydrated cement phases in concrete and
atmospheric carbon dioxide (CO 2 ), where the phases
react with the CO 2 , absorbing some of it into the
exposed surfaces. By reabsorbing atmospheric CO 2 ,
concrete pavements can partially offset their environmental
impact of CO 2 generation that occurs during
the manufacture of cement. Gajda (2001) gathered
data on the amount of CO 2 that could be absorbed by
concrete based on more than 1,000 samples. Figure
6.4 shows one sample that has carbonated to a depth
of 18 mm. Carbonation rates varied depending on the
strength of the concrete and cement content, but the
average rate of carbonation for uncoated concrete was
found to be 4.23 mm/yr 0.5 . He further estimated that,
on average, concrete produced in the United States
could absorb about 274,000 metric tons of atmospheric
CO 2 in the first year after placement. Although
the rate of carbonation will slow with time, it is important
to know that a measurable amount of CO 2 will be
sequestered by a concrete pavement while in service.
As is discussed in Chapter 8, significant additional
amounts of CO 2 can be absorbed through carbonation
at the end of a pavement’s life, particularly if it is
crushed as part of a recycling operation.
Run-Off and Leachate
After a rainstorm, run-off from the pavement surface
can carry pollutants with it, most of which originated
from vehicles that used the pavement and not from the
pavement material itself (Santero et al. 2011b). The
use of a pervious concrete surface (currently applicable
for low traffic volume pavements, parking areas, and
shoulders) can help mitigate some of this effect by
preventing most surface run-off from directly entering
streams and lakes (Borst et al. 2010). Instead, natural
processes degrade the pollutants as the water slowly
passes through aggregate and soil. Further, pervious
concrete surfaces will prevent run-off warmed by a hot
pavement surface from rapidly entering surface waters,
thus helping to maintain a cool water temperature
which is necessary for some species’ survival. As pervious
concrete is most often used in urban areas, Chapter
9 includes a more detailed discussion on this topic.
Santero et al. (2011b) also noted that research has
been inconclusive related to run-off or leachates from
recycled materials. It is known that when concrete is
recycled and stockpiled, run-off from the stockpiles
initially has a pH of 9 or 10, but the pH diminishes
within weeks as exposed cement grains and soluble
cement paste phases react (ACPA 2009). Additional
discussion on the use of recycled concrete is presented
in Chapter 8.
Figure 6.4 Depth of carbonation determined by the
phenolphthalein test (pink two-thirds of the sample
is not carbonated (Gajda 2001)
Traffic Delays
Traffic delays incurred during pavement maintenance
and rehabilitation (see Figure 6.5) greatly influence
vehicle fuel consumption. Santero et al. (2011a)
hypothesize that traffic delays could be a much greater
portion of a pavement’s environmental impact than
construction materials and equipment. As a result, it
is recognized that the environmental impacts of traffic
delay resulting from future maintenance and rehabilitation
activities should be included in the environmental
assessment, and work continues to characterize this
impact (Santero et al. 2011c). The inclusion of this
Sustainable Concrete Pavements A Manual of Practice
Ch. 6. IMPACT OF THE USE PHASE 51

impact would further demonstrate the environmental
savings that can be incurred through long-life pavements
that have little need for future lane closure in
support of maintenance/rehabilitation activities.
3. Summary
Studies have recognized the importance of considering
the use phase in sustainable design, yet often it
is largely ignored. Pavement designers, contractors,
and owners may not have influence on the types of
vehicles that use pavements. However, with proper
consideration during design and construction and
the adoption of an aggressive concrete preservation
strategy, concrete pavements can be constructed and
maintained in a smooth condition, reducing fuel
consumption and related emissions. Over the life
cycle, small improvements in fuel efficiency incurred
due to the inherent stiffness of concrete pavements
may significantly reduce the environmental impact
of pavements. Further, the relatively high reflectivity
of concrete will help reduce the heat island effect,
reduce the energy needed for artificial illumination,
and through radiative forcing reduce global warming,
further enhancing environmental performance during
the use phase. Other factors that should be considered
include carbonation, run-off and leachate generation,
and traffic delays incurred during future maintenance
and rehabilitation activities. Work is under way to
better characterize the environmental impacts that are
incurred through the use phase and to determine how
these can more easily be included in environmental
life-cycle assessment. Indications are that the use phase
has the greatest impact of all life-cycle phases and thus
must be considered in sustainable design.
4. References
American Association of State Highway and Transportation
Officials (AASHTO). 2009. Rough Roads Ahead-
Fix Them Now or Pay for It Later. Washington, D.C.:
AASHTO (http://roughroads.transportation.org/Rough­
Roads_FullReport.pdf; accessed on August 8, 2011)
American Concrete Pavement Association (ACPA).
2009. Recycling Concrete Pavements. Engineering Bulletin
043P. Skokie, IL: ACPA.
Akbari, H., and S. Menon. 2008. Global Cooling:
Increasing World-wide Urban Albedos to Offset CO 2
.
Lawrence Berkeley National Laboratory. Arthur
Rosenfeld California Energy Commission. Pavement
Interactive. (http://pavementinteractive.org/index.
php?title=Global_Cooling:_Increasing_World-wide_
Urban_Albedos_to_Offset_CO2; accessed August 8,
2011)
Akbarian, M. 2011. When the Rubber Meets the Road.
Life Cycle Analysis Research Brief. Cambridge, MA:
Concrete Sustainability Hub, Massachusetts Institute of
Technology.
Ardekani, S., and P. Sumitsawan. 2010. “Effect of
Pavement Type on Fuel Consumption and Emissions
in City Driving.” Concrete Sustainability Conference.
National Ready Mixed Concrete Association.
Bennett, C.R., and I.D. Greenwood. 2003. Volume 7:
Modeling Road User and Environmental Effects in HDM-4.
Version 3.0, International Study of Highway Development
and Management Tools (ISOHDM). World Road
Association (PIARC). ISBN: 2-84060-103-6.
Figure 6.5 Traffic delays caused by construction
(photo courtesy of Jim Cable, FHWA)
Borst, M., A. Rowe, E. Stander, and T. O’Connor.
2010. Surface Infiltration Rates of Permeable Surfaces: Six
Month Update (November 2009 through April 2010).
EPA/600/R-10/083. Washington, D.C.: U.S. Environmental
Protection Agency.
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Chatti, K. 2010. “Effect of Pavement Conditions on
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54 Ch. 6. IMPACT OF THE USE PHASE Sustainable Concrete Pavements A Manual of Practice

Chapter 7
CONCRETE PAVEMENT RENEWAL
Tom Van Dam
Preservation and rehabilitation play an important role
in ensuring pavement longevity while maintaining
the highest level of serviceability. Long-lasting pavements
reduce future investments in new materials and
construction, thus minimizing economic, environmental,
and social impact over the life cycle. Further,
a well maintained concrete pavement will remain in a
smooth, safe, and quiet condition for a greater portion
of its life, thus increasing the fuel efficiency of vehicles
and reducing crashes that adversely impact the community.
As such, renewal directly contributes to the
sustainability of the concrete pavement.
This chapter briefly discusses renewal strategies that can
be applied to concrete pavements to effectively maintain
serviceability over the design life. The two primary
strategies that are discussed are preventive maintenance
and rehabilitation. Preventive maintenance is a planned
strategy employing treatments that extend pavement
life, generally without increasing structural capacity.
Pavement rehabilitation adds some structural capacity,
usually through the application of additional pavement
thickness in the form of an overlay. Timely and appropriate
preventive maintenance and rehabilitation can
enhance sustainability over the concrete pavement life
cycle.

1. Pavement Renewal Concepts
Although many treatments and strategies are available
that contribute to concrete pavement renewal, they can
generally be classified under preventive maintenance
or rehabilitation. Preventive maintenance is a planned
strategy employing cost-effective treatments (e.g.,
patching, joint sealing, diamond grinding, and so on)
that extend pavement life without increasing structural
capacity (Smith, Hoerner, and Peshkin 2008). Unlike
preventive maintenance, pavement rehabilitation adds
some structural capacity, usually through the application
of additional pavement thickness in the form of an
overlay (Harrington et al. 2008).
Figure 7.1 graphically illustrates a typical pavement
life, with pavement “condition” (e.g., level of distress,
roughness, structural capacity, and so on) plotted on
the vertical axis and time (or traffic) plotted on the
horizontal axis. The curved line represents pavement
performance over time, showing initially that pavement
condition slightly decreases with time as the
pavement ages and is subjected to traffic. After the initial
phase of the pavement life, performance decreases
at an increasing rate before finally leveling off once it
has reached a poor condition.
Figure 7.1 also shows typical “windows” in which
preventive maintenance and rehabilitation are applicable.
As can be seen, preventive maintenance is only
applicable when the pavement is in relatively good
condition and has significant remaining life. Thus,
a common precept is that preventive maintenance
is used to keep good pavements in good condition.
In some cases maintenance may be required on high
traffic lanes only, in which case detailing should avoid
elevation differences between lanes. Pavement rehabilitation
is appropriate after the pavement condition has
dropped to a point where it is no longer effective to
apply preventive maintenance. As can also be seen in
Figure 7.1, after the pavement condition has dropped
to a certain level—the pavement life is basically “used
up”—the only suitable treatment is reconstruction.
Figure 7.2 illustrates the monetary impact of treatments
applied at various pavement condition levels,
as represented by a generalized pavement condition
rating (PCR). It shows that $1.00 spent to maintain a
good pavement (PCR 60 to 100) in good condition is
equivalent to spending $4.80 to $7.00 on a pavement
having a PCR of 50 to 60. This cost jumps to $20.00
at a PCR of 40 to 50, and to $48.00 at a PCR less
than 40, illustrating the cost effectiveness of properly
applied preventive maintenance treatments.
The effects of preventive maintenance and rehabilitation
are illustrated in Figure 7.3. As can be seen, each
application of a preventive maintenance treatment provides
a small increase in condition, often translating to
increased smoothness. Thus, the application of timely
and appropriate preventive maintenance treatments
will keep a smooth pavement smooth for an extended
period of time. This is not only cost effective for the
agency responsible for maintaining the pavement but,
as discussed in Chapter 6, it also reduces the vehicle
operating costs as well as the environmental impact of
vehicles operating on the pavement.
Good
Preventive
Maintenance
Pavement Preservation Window
Pavement Condition
Rehabilitation
Maintenance
Reconstruction
60-100 Each $1.00 spent at PCR 60-100
PCR
50-60
Costs $4.80 to $7.00 at PCR 50-60
40-50 Costs $20.00 at PCR 40-50
Poor
0-40 Costs $48.00 at PCR 0-40
Time
Figure 7.1 Typical pavement performance
curve showing ideal times for the application
of pavement preservation, rehabilitation, and
reconstruction (Smith, Hoerner, and Peshkin 2008)
10 15 20
Years (age)
Figure 7.2 Comparison of treatment costs at
different pavement condition ratings (PCRs)
( Zimmerman and Wolters 2003)
56 Ch. 7. CONCRETE PAVEMENT RENEWAL Sustainable Concrete Pavements A Manual of Practice

At some point, preventive maintenance alone may be
incapable of maintaining the pavement in a smooth
condition indefinitely, and therefore the application of
a rehabilitation treatment is needed to restore structural
capacity. This is illustrated in Figure 7.3, where a
large improvement in condition is realized through the
application of the rehabilitation treatment. However,
the underlying condition of the original pavement
affects the life of the rehabilitation; thus, after rehabilitation,
pavement condition may decrease at a faster
rate than it does for a newly constructed pavement.
In summary, the concept of concrete pavement
renewal requires that preventive maintenance and
rehabilitation techniques be employed, using the right
treatment at the right time. To be cost effective while
reducing life-cycle environmental impact, preventive
maintenance treatments are applied to pavements in
generally good condition, keeping them smooth while
extending life. Over time, the structural capacity of
most pavements will need to be restored or increased,
at which juncture the use of pavement rehabilitation
techniques will be the best approach.
2. Pavement Evaluation
Overview
Determining “the right time” and the “right strategy”
(maintenance or rehabilitation) requires a thorough
pavement evaluation (Smith, Hoerner, and Peshkin
2008). Not understanding the pavement condition can
result in the application of an inappropriate treatment
and, consequently, either an early failure or wasteful
Good
Pavement Condition
Poor
Preventive
Maintenance
Rehabilitation
Time
Figure 7.3 Illustration of typical impacts of
preventive maintenance and rehabilitation on
concrete pavement condition (Smith, Hoerner, and
Peshkin 2008)
over-design. For example, a recent study of economic
and environmental life-cycle performance of concrete
pavements found that when the life of a rehabilitation
treatment was not fully utilized, it resulted in significant
environmental cost (Van Dam et al. 2011). Thus,
the first step in any preventive maintenance/rehabilitation
project is an evaluation of the existing conditions.
A typical concrete pavement evaluation will consist
of the following steps (Smith, Hoerner, and Peshkin
2008):
1. Review of historical data and records – This should
include a review of design reports, construction
plans and records, materials and soils properties,
past performance and maintenance records,
past and anticipated future traffic, and climatic
conditions.
2. Initial site visit and assessment – This consists of an
initial visit to assess general conditions and help
scope the future evaluation and includes general
distress observations, an assessment of roughness,
particularly sags and swells, and observation of
moisture problems.
3. Field testing activities – These may include detailed
distress and drainage surveys, nondestructive
deflection testing, roughness and friction testing,
and field sampling and testing.
4. Laboratory materials characterization – This may
include determining the strength and stiffness of
concrete and bound layers, petrographic analysis of
concrete, density, and gradation analysis. The focus
is on using the data to determine the overall pavement
condition, focusing on causative effects and
uniformity over the project length.
Upon completion of the evaluation, a determination
will be made whether the pavement is in good condition,
as defined by the owner, and possesses adequate
structural capacity to be suitable for preventive maintenance,
or whether the conditions are such that
structural improvement is required through the use of
rehabilitation. It is important to note that, if the pavement
is deteriorating due to a materials-related distress
(MRD) mechanism, such as alkali-silica reactivity or
freeze-thaw damage, it may not be a good candidate
for preventive maintenance strategies that do not
address the underlying distress mechanism.
Sustainable Concrete Pavements A Manual of Practice
Ch. 7. CONCRETE PAVEMENT RENEWAL 57

The following sections will discuss preventive maintenance
and rehabilitation treatments, and how their use
results in increased sustainability over the life cycle.
3. Preventive Maintenance
Treatments
Concrete pavement preservation treatments include
the following (Smith, Hoerner, and Peshkin 2008):
• Slab stabilization
• Partial-depth repair
• Full-depth repair
• Use of precast panels in full-depth repairs
• Retrofitted edge drains
• Load transfer restoration
• Diamond grinding and grooving
• Joint resealing and crack sealing
Not all projects will include all treatments. The most
common treatments that address ride quality are partial-
and full-depth repairs, load transfer restoration,
and diamond grinding. These are discussed below.
Cross stitching may be conducted on newer pavements
that have early-age cracks (ACPA 2006). When thin
bonded concrete overlays are constructed primarily to
restore ride quality rather than add structural capacity,
they may be considered as preventive maintenance
projects; overlays are described in detail under the
Rehabilitation section of this chapter.
Partial-Depth Repair
Partial-depth repairs are used to repair surface distress
that is isolated in the top one-third of the slab, restoring
ride quality and allowing for effective sealing of
joints (Frentress and Harrington 2011). This type of
distress is often found in the vicinity of joints and is
most often caused by the infiltration of incompressible
material into the joint that results in spalling as
the joint closes during warmer weather. Poor concrete
consolidation, localized areas of weak concrete, corrosion
of reinforcing steel, and the use of joint inserts
also contribute to the formation of surface distress that
can be addressed through partial-depth repairs. Traffic
is often a contributing factor, as joint displacement
can “pinch” the concrete at the surface and dislodge
concrete weakened by other factors.
The conventional repair sequence includes the following
(Smith, Hoerner, and Peshkin 2008):
1. Repair boundaries are determined, ensuring that all
the deteriorated/delaminated concrete is identified
for removal.
2. Concrete is removed using partial-depth saw cuts
to define repair boundaries and light-weight jack
hammers to carefully remove the concrete from
repair area.
3. Repair area is prepared by final removal of loose
material and cleaned using sand-blasting and
air-blasting.
4. Joint is prepared, including insertion of a compressible
material into the joint to prevent intrusion
of the repair material.
5. For some repair materials, bonding grout/agent
must be applied immediately prior to placement of
the repair material.
6. The patch material is placed in accordance with
manufacturer’s instructions.
7. The patch is cured for the specified time, often
using a white pigmented membrane curing
compound. Blankets may be required in cooler
weather.
A recent publication discusses how concrete removal
can be conducted quite efficiently using modern milling
machines in which rotating carbide teeth grind
away the existing concrete to the desired depth, leaving
a rough substrate that facilitates bonding of the
repair material (Harrington et al. 2011). See Figure
7.4. This technique has been used successfully in a
number of states, creating cost-effective, long-lasting
repairs.
Several materials are available for partial-depth repairs,
with the choice being driven by the desired time to
opening. Long-lasting, durable repairs have been created
using portland cement-based products, although
if the required time to opening is less than 12 hours,
often proprietary cementitious- or polymeric-based
materials are used (Smith, Hoerner, and Peshkin 2008,
58 Ch. 7. CONCRETE PAVEMENT RENEWAL Sustainable Concrete Pavements A Manual of Practice

Harrington et al. 2011). The selection of the repair
material is based on multiple factors that are assessed
as part of operations and maintenance.
Full-Depth Repair
Full-depth repairs, including full slab replacements,
are used to repair various types of structural distress
including transverse cracking, corner breaks, longitudinal
cracking, severely deteriorated joints (distress
extends deeper than one-third the slab depth), blowups,
and punch-outs. These distresses compromise
the structural integrity of the pavement system, and
the use of full-depth repairs restores the lost capacity
while improving ride quality. If the distress is present
through a large percentage of the project, full-depth
repairs may not be cost effective. Instead, a structural
rehabilitation using an overlay might be more effective
and potentially result in a more sustainable solution
(Smith, Hoerner, and Peshkin 2008).
Full-depth repairs of jointed concrete pavement are
accomplished according to the following steps:
1. Repair boundaries are identified, ensuring that the
entire potential extent of deterioration is incorporated.
Figure 7.5 illustrates that often the distress
at the bottom of the slab extends beyond what is
visible at the surface, and the effectiveness of the
repair is dependent on the complete removal of
deteriorated concrete.
2. The concrete is sawed the full depth of the slab,
ensuring a smooth face for restoration of load
transfer devices. Multiple saw cuts may be used to
facilitate removal of the concrete.
3. Concrete is removed in a way that minimizes
disruption to adjacent concrete and the underlying
base. The lift-out method, in which lift pins
are attached through drilled holes, has been found
to be most effective, although other methods have
also been successful.
4. The repair area is prepared by removal of loose
material, replacing it with compacted materials of
similar properties or with concrete. As compaction
within the confined repair area is difficult, replacement
with concrete is often the best approach.
5. Load transfer at the transverse edges of the repair
is restored through the use of steel dowels, which
are grouted into holes created using gang-mounted
drills.
6. Concrete is placed and finished in accordance with
appropriate specifications. Typically conventional
concrete can be used, although often a high-early
or even a very high-early strength mixture can
be selected. In general, it is best to use accelerated
strength gain mixtures only if the constraints
of the project dictate that early opening to traffic
is required, as the economic and environmental
impact of the repair material can be increased if
early strength gain is specified. Use of recycled
materials may help to balance this negative impact.
7. Curing is typically accomplished using a white
pigmented curing compound. Blankets may be
required in cooler weather and/or if accelerated
strength gain is desired.
Existing
Joint
Visual deterioration of surface
Dowel bar
Potential deterioration at bottom of slab
Figure 7.4 Damaged material has been milled out
in a partial-depth repair (photo courtesy of Dale
Harrington, Snyder and Associates)
Figure 7.5 Illustration of distress extent, with distress
at the bottom of the slab extending beyond that
observed at the surface (Smith, Hoerner, and
Peshkin 2008)
Sustainable Concrete Pavements A Manual of Practice
Ch. 7. CONCRETE PAVEMENT RENEWAL 59

Full-depth repairs are used when deterioration extends
beyond one-third the slab depth and safety and ride
quality are compromised. Well constructed full-depth
repairs should last for the life of the concrete pavement,
effectively restoring structural integrity and ride
quality, and are thus an important treatment used to
maintain concrete pavements over the life cycle.
Load Transfer Restoration
The restoration of load transfer is a technology that has
had a significant impact on improving the ride quality
of concrete pavements throughout the United States.
It was not uncommon in the past to construct jointed
plain concrete pavement (JPCP) without load transfer
devices, with the assumption that aggregate interlock
would be sufficient to maintain load transfer with
shorter joint spacing. Unfortunately, it has been found
that JPCPs constructed without load transfer devices
are susceptible to joint faulting, resulting in poor ride
quality even though the pavement is otherwise sound.
Further, in some jointed concrete pavements with load
transfer devices, faulting has occurred as heavy traffic
has eventually degraded the ability of the joint to
transfer load. In either case, load transfer restoration
has provided an avenue to restore the ability of load
to be shared across a joint, minimizing deflection and
reducing cracking, thus positively affecting remaining
life. Once load transfer is restored, the primary mechanism
causing faulting is eliminated. Assuming drainage
is also addressed using edge drains, and that the slabs
have been restored to desired elevations, the pavement
can then be diamond ground to improve ride quality.
Load transfer restoration is illustrated in Figure 7.6.
The current practice for restoring load transfer is as
follows (Smith, Hoerner, and Peshkin 2008):
joint is then caulked to prevent intrusion of repair
material
3. A dowel bar is placed in each slot. The dowel bar
is typically on a chair, coated with a bond breaker
and capped with an expansion cap on one or both
ends. A compressible insert is located at the bar
center to establish the joint in the repair. Figure 7.7
shows dowel bars adjacent to prepared slots, waiting
to be placed.
4. Repair material is placed in the slot according to
the manufacturer’s recommendations and consolidated
with a small, spud-type vibrator. The repair
is then finished and cured to minimize shrinkage.
The repair material is critical to the success of this
treatment. Most materials that are suitable for partial-depth
repair are suitable for this application.
Figure 7.6 Schematic illustration of load transfer
restoration (ACPA 2006)
1. Slots for dowel bars are created using gangmounted
saw blades mounted on specially
designed slot-cutting machines. Production rates
exceeding 2,500 slots per day are possible using
this method.
2. Each slot is prepared using a lightweight jack hammer
to carefully scalp the concrete from the slot
and then using a hammerhead to flatten the bottom
of the slot. The slot is then cleaned by sandblasting
and air-blasting to provide a surface with
which the repair material can bond. The existing
Figure 7.7 Dowel bars on chairs with end caps and
compressible inserts in place ready to be inserted
into prepared slots (IGGA 2010)
60 Ch. 7. CONCRETE PAVEMENT RENEWAL Sustainable Concrete Pavements A Manual of Practice

With the advent of slot-cutting machines, which
ensure good productivity and quality, load transfer
restoration has become a popular operation to address
poor load transfer that is common in undoweled JPCPs
and in older pavements in which load transfer has
been lost. In combination with diamond grinding, load
transfer restoration can be used to effectively maintain
a concrete pavement in a smooth condition over its
design life.
Diamond Grinding
Diamond grinding is applied to a concrete pavement
after partial- and full-depth repairs and load transfer
restoration, as well as slab stabilization and drainage
retrofitting. Using gang-mounted, closely-spaced
diamond saw blades, diamond grinding uniformly
removes a thin layer of concrete, restoring pavement
ride quality while improving skid resistance. This
treatment removes faulting, wheel path wear, surface
irregularities, and polished surface texture, replacing
them with a uniform surface that can be as smooth,
quiet, and safe as the originally constructed surface.
Figure 7.8 shows a close-up of a diamond ground
surface, showing how it is renewed without the need
to add any new material.
Diamond grinding has been in use for decades, having
been pioneered in California where it was first used
in 1965. California continues to routinely apply this
technique, finding that a ground pavement will maintain
its smoothness for 16 to 17 years before the need
to regrind, with some projects receiving three successive
grindings over their design life in regions without
studded tires or chains (Stubstad et al. 2005).
Figure 7.8 Diamond ground surface after years of
service (photo courtesy of The Transtec Group)
In general, pavements with faulting in excess of 0.125
in., IRI roughness of 63 to 90 in./mi, or wheel path
wear up to 0.375 in. are good candidates for diamond
grinding. More specifically, the following guidelines
apply (Smith, Hoerner, and Peshkin 2008):
• Exceedingly rough pavements having an IRI in
excess of 190 in./mi may be too rough to be successfully
ground in a cost-effective manner. In such
cases, rehabilitation through the use of an overlay
may be more appropriate (Correa and Wong 2001).
• Severe drainage problems must be addressed prior
to diamond grinding.
• Structural distress must be repaired prior to diamond
grinding.
• If load transfer efficiencies are below 60 percent,
load transfer restoration must be completed prior to
diamond grinding.
• The harder the aggregate, the more difficult and
expensive it is to grind. In some instances, it may
be cost prohibitive to effectively grind a concrete
made with extremely hard aggregates.
• If there is need for significant full-depth repair and
slab replacements, the structural life of the pavement
may be near its end and thus diamond grinding
would not be a good option.
• As with other preventive maintenance treatments,
if the pavement is deteriorating due to a materialsrelated
distress (MRD) mechanism, such as alkalisilica
reactivity or freeze-thaw damage, it may not
be a good candidate for diamond grinding.
As a treatment that can improve overall ride quality
and skid resistance in a cost-effective manner,
diamond grinding has the potential to significantly
improve vehicle fuel efficiency and safety, thus contributing
directly to improved sustainability. Also, there
have recently been efforts to remove asphalt overlays
from some concrete pavements that were overlaid
primarily to address ride quality issues (IGGA ND).
These pavements then undergo preventive maintenance
treatments and diamond grinding, returning
them into service as renewed concrete pavements. This
has the advantage of minimal future maintenance costs
as well as increased reflectivity, thus lowering life-cycle
environmental impact.
Sustainable Concrete Pavements A Manual of Practice Ch. 7. CONCRETE PAVEMENT RENEWAL 61

Summary
In summary, preventive maintenance plays a critical
role in keeping good pavements in good condition.
Treatments such as partial- and full-depth repair
replace deteriorated concrete while restoring ride
quality and structural integrity of the pavement. Load
transfer restoration slows the progression of future
faulting and, combined with diamond grinding which
eliminates existing faulting, results in the long-term
restoration of ride quality. Preventive maintenance
is thus a cost effective, low-environmental impact
approach to reducing vehicle operating costs and associated
emissions over the pavement life cycle.
4. Rehabilitation
As defined by Harrington et al. (2008), pavement
rehabilitation through an overlay can be considered as
minor rehabilitation or major rehabilitation, differentiated
primarily by the thickness of the overlay and the
degree to which structural capacity is increased. As
mentioned previously, thin bonded concrete overlays
are constructed primarily to restore surface quality
and are generally considered to be preventive maintenance
projects. Bonded concrete overlays may also be
considered minor rehabilitation in that they generally
add some structural capacity to pavements. Unbonded
concrete overlays, which are generally 4-in. thick or
more, comprise minor and major rehabilitation projects,
involving structural enhancements that extend
service life.
Concrete overlays can be placed on existing concrete,
asphalt, and composite pavements. This chapter,
however, focuses on overlays of existing concrete
pavements. Various pavement conditions for which
different types of concrete overlays are appropriate are
illustrated in Figure 7.9.
Bonded Concrete Overlays
In certain circumstances, a bonded concrete overlay
provides a good treatment option to eliminate surface
defects (e.g., extensive scaling, poor aggregate friction
characteristics, and so on), infill a milled section,
and/or increase the structural capacity of an existing
concrete pavement, while meeting vertical clearance
requirements. In general, the existing concrete pavement
must be in good structural condition. The keys
to successful use of a bonded concrete overlay are as
follow (Harrington et al. 2008):
• The existing substrate pavement surface must be
thoroughly prepared and cleaned to enhance the
bond between it and the overlay.
• The coefficient of thermal expansion of the overlay
concrete must be similar to that in the substrate
concrete.
• Working cracks in the existing pavement must be
repaired, or the overlay should be sawed over them to
prevent uncontrolled reflective cracking in the overlay.
• Existing joints must be in fair to good condition or
repaired.
• Joint sawing must be done promptly following construction
of the overlay.
• Transverse joints in the overlay must be sawed full
depth plus 0.5 in., whereas longitudinal joints must
be sawed to half the overlay thickness.
• Joints in the overlay must align with those in the
underlying pavement.
• The width of the transverse joints in the overlay must
be the same or greater than the width of the crack in
the transverse joints in the underlying pavement.
• Curing compound must be applied in a timely and
thorough fashion.
As the name implies, a good bond between the overlay
and the existing substrate pavement must be achieved
during construction and must be maintained during the
life of the pavement, as the loss of bond will result in
premature failure of the overlay. Thus, great care must
be exercised during construction to ensure that the
substrate is properly prepared, that construction is done
as specified, that the joints are sawed promptly and to
the correct depth, and that curing is conducted expeditiously
and with care. The following is a summary of
the bonded concrete overlay process (Harrington et al.
2008):
1. Pavement evaluation – The pavement should be
thoroughly evaluated to ensure that it is a good candidate
for a bonded concrete overlay. In general, it
must be structurally sound, relatively free of distress,
and must not be suffering from an MRD.
62 Ch. 7. CONCRETE PAVEMENT RENEWAL Sustainable Concrete Pavements A Manual of Practice

2. Overlay design – Bonded concrete overlays are typically
2- to 5-in. thick, and thickness is commonly
designed using the AASHTO (1993) Guide for
Design of Pavement Structures, although the use of
the new AASHTO Darwin-ME design will continue
to grow in popularity. Conventional concrete mixtures
have been successful in constructing bonded
concrete overlays. Joint design must match the
existing concrete pavement.
3. Pre-overlay repair – Pre-overlay repair is essential
for the successful performance of bonded concrete
overlays. Table 7-1 provides recommendations
regarding the type of distresses that require repair
and suitable treatments. As the overlay is intimately
bonded to the substrate, existing distress will have
a tendency to reflect through unless addressed.
After repairs are conducted, the surface should
be roughened and thoroughly cleaned to enhance
bonding.
4. Construction – Key elements of construction
include concrete placement, curing, and joint
sawing. Although conventional construction
techniques are used, curing is especially critical
because the thinness of the layer gives it a
high surface area to volume ratio, making it very
susceptible to moisture loss. Also, as the underlying
pavement will continue to move in response to
changing temperatures, it is critical that joint sawing
be initiated as soon as possible to minimize the
chance for random cracking.
When well designed and constructed correctly, a
bonded overlay will extend the life of a concrete pavement
for decades, providing a sustainable solution to
correct specific problems in an existing structurally
sound concrete pavement. See Figure 7.10.
Table 7.1 Pre-Overlay Repair Recommendations for
Bonded Concrete Overlays (Harrington et al. 2008)
Existing
Pavement Distress
Spot Repairs to Consider
Reflective cracking is likely if no
Random cracks repairs are made; use crack cages or
full-depth repairs for severe cracks
Faulting
Slab stabilization
Pumping
Slab stabilization
Asphalt patch
Replace with concrete patch to
ensure bonding
Joint spalling Partial-depth repair
Scaling
Remove with cleaning
Figure 7.10 Bonded overlay
Existing pavement condition
before treatment
Preventive
maintenance
Minor
rehabilitation
Bonded
on
Concrete
Major
rehabilitation
Unbonded
on
Concrete
Reconstruction
Bonded
on Asphalt
or
Composite
Unbonded
on Asphalt
or
Composite
Time
Figure 7.9 Typical applications for bonded and unbonded concrete overlays on existing concrete and
asphalt/composite pavements (Harrington et al. 2008)
Sustainable Concrete Pavements A Manual of Practice Ch. 7. CONCRETE PAVEMENT RENEWAL 63

Unbonded Concrete Overlays
Unbonded concrete overlays have been successfully
used in the rehabilitation of concrete pavements for
decades and are viable treatments to address concrete
pavements with some structural deterioration. Since
the overlay is essentially designed as a new concrete
pavement, it can restore load-carrying capacity, providing
a new riding surface and extending pavement life.
The overlay has an effective service life similar to a
newly constructed concrete pavement.
Unbonded concrete overlays are typically 6- to 11-in.
thick, depending on the anticipated traffic and the
condition of the underlying pavement (Harrington et
al. 2008). As the name implies, the overlay is purposely
separated from the underlying slab; that is, it is
designed independently, considering the existing pavement
as a base. As such, unbonded concrete overlays
do not require extensive pre-overlay repair, nor do
joints need to be matched with those in the underlying
slab. The keys to effectively using an unbonded
overlay are as follow (Harrington et al. 2008):
• The existing pavement is in poor condition but is
stable and uniform. Material-related distress (MRD)
is not a concern as long as continued expansion
will not result in blow-ups.
• Ideal applications are existing pavements that
require significant improvement in structural capacity
and/or serviceability (ride quality, skid resistance,
and so on).
• Full-depth repairs are conducted only in isolated
locations where structural integrity must be
restored.
• Traditionally, the overlay is separated from the
underlying pavement through the use of a thin
(1-in.) asphalt layer. Recent use of a thick, nonwoven
geotextile as the separation layer has been
promising, and this strategy is likely to grow in
acceptance (Rasmussen and Garber 2009).
• Faulting is generally not a problem if it is 0.38 in.
or less and if a 1-in. thick asphalt separation layer
is used.
• Joint sawing must be done promptly following construction
of the overlay.
• Shorter joint spacing than normal is often needed
to reduce stresses due to temperature curling.
• Joints do not need to be matched or purposely
mismatched.
As the overlay is isolated from the underlying pavement,
this treatment is ideal for concrete pavements
that are near or at the end of their life but can still
provide good, uniform support for the new overlay.
The following is a summary of the unbonded concrete
overlay process (Harrington et al. 2008):
1. Pavement evaluation – The existing pavement
should be evaluated to ensure that it can provide
good uniform support for the unbonded concrete
overlay and, if not, to determine what actions are
needed to obtain uniformity. Although a candidate
pavement can be suffering MRD, the evaluation
should confirm that future expansion will not result
in blow-ups of the underlying pavement in time.
2. Overlay design – Unbonded concrete overlays are
typically 6- to 11-in. thick, and thickness is commonly
designed using the AASHTO (1993) Guide
for Design of Pavement Structures, although the use
of the new AASHTO mechanistic-empirical design
will continue to grow in popularity. The separation
layer has traditionally been a 1-in. thick hot-mix
asphalt surface course, although the use of thick,
nonwoven geosynthetics is showing promise. Conventional
concrete mixtures have been successfully
used in constructing unbonded concrete overlays.
Joint design includes the use of dowel bars for
unbonded overlays 8-in. thick or greater and the
use of short joint spacing to minimize temperature
curling stresses. Typical joint spacing is shown in
Table 7-2. Drainage must be considered to avoid
damage to the asphalt separation layer. Edge support
should be provided with tied concrete shoulders
in lieu of widened overlay slabs to avoid high
curling stresses.
3. Pre-overlay repair – Typically only distresses resulting
from major loss of structural integrity require
pre-overlay repair for unbonded concrete overlays.
Table 7-3 provides recommendations regarding the
type of distresses that require repair and suitable
treatments.
64 Ch. 7. CONCRETE PAVEMENT RENEWAL Sustainable Concrete Pavements A Manual of Practice

4. Construction – Key elements of construction include
concrete placement, curing, and joint sawing.
Although conventional construction techniques are
used, curing is especially critical if a relatively thin
unbonded overlay is used because of the high surface
area to volume ratio, making it very susceptible
to moisture loss. Also, it is critical that joint sawing
be initiated as soon as possible to minimize the
chance for random cracking, as the underlying high
level of restraint and stiff support will result in rapid
development of tensile stresses.
Unbonded concrete overlays continue to enjoy popularity
as an excellent strategy for the rehabilitation of
concrete pavements nearing the end of their useful life.
See Figure 7.11. The overlay has all of the sustainability
advantages inherent in a newly constructed concrete
pavement, without the added economic and environmental
costs associated with crushing and removing
the existing pavement and transporting and compacting
new base material. In effect, the agency retains and
builds on the equity invested in the original pavement.
The amount of fuel used to construct an overlay
is reportedly considerably less than that used for
new construction, thereby reducing the impact of the
rehabilitation. Further, traffic delays during construction
are minimized, as the existing pavement provides
an excellent working platform, minimizing delays due
to weather that can be problematic when removing the
existing pavement and constructing the base. Finally,
since unbonded concrete overlays are typically thinner
than a newly constructed pavement designed for the
same traffic loading, unbonded overlays provide additional
economic and environmental benefits through
the use of less material. In combination, these factors
make unbonded overlays a very sustainable treatment
option to rehabilitate pavements nearing the end of their
useful life.
Table 7.2 Recommended Transverse Joint Spacing
for Unbonded Concrete Overlay (Harrington et al.
2008)
Unbonded Resurfacing
Thickness
Maximum Transverse
Joint Spacing
< 5 in. (125 mm) 6 x 6 ft (1.8 x 1.8 m) panels
5–7 in. (125–175 mm)
> 7 in. (175 mm) 15 ft (4.6 m)
Spacing in feet =
2 times thickness in inches
Table 7.3 Pre-Overlay Repair Recommendations
for Unbonded Concrete Overlays (Harrington et al.
2008)
Existing Pavement
Condition
Faulting 0.25–0.38 in.
(6–10 mm)
Faulting > 0.38 in.
(10 mm)
Significant tenting
Badly shattered slabs
Significant pumping
Severe joint spalling
CRCP with punchouts
or other severe damage
Possible Repairs to
Consider
None
Thicker separation layer
Full-depth repair
Full-depth repair
Full-depth spot repair and
drainage improvements
Clean
Full-depth repair
5. Summary
The application of proper concrete pavement preventive
maintenance and rehabilitation strategies is essential to
extend the life of a concrete pavement while ensuring
that it remains in a structurally sound, smooth, and safe
condition over its life cycle. Applying the right strategy
at the right time contributes to the overall sustainability
of the pavement by ensuring it meets or exceeds its
Figure 7.11 Unbonded overlay
Sustainable Concrete Pavements A Manual of Practice Ch. 7. CONCRETE PAVEMENT RENEWAL 65

design life with minimum impact. Not only are economic
savings maximized, but the negative economic
and environmental impacts of vehicle operations are
minimized as well, while the pavement is maintained
in a safe condition. The techniques described in this
chapter offer a variety of preventive maintenance tools
to address deterioration that results from usage and
time. In particular, the use of load transfer restoration
and diamond grinding has been shown to extend
the life of a concrete pavement in a very cost-effective
and environmentally friendly manner. As a concrete
pavement nears the end of its useful life, it can be
rehabilitated through the use of an unbonded overlay,
essentially constructing a new concrete pavement on
the surface of the old pavement. Thus, an engineer
skilled in the use of these and other strategies in the
pavement preventive maintenance and rehabilitation
toolkit can sustainably manage concrete pavements
into perpetuity.
6. References
American Association of State Highway and Transportation
Officials (AASHTO). 1993. Guide for Design of
Pavement Structures. Washington, D.C.: AASHTO.
American Concrete Pavement Association (ACPA).
2006. Concrete Pavement Field Reference–Preservation
and Repair. Report EB239P. Skokie, IL: ACPA.
Correa, A., and B. Wong. 2001. Concrete Pavement
Rehabilitation–Guide for Diamond Grinding. Report No.
FHWA-SRC-1/10-01(5M). Washington, D.C.: FHWA.
Frentress, D.P, and D.S. Harrington 2011 (draft). Guide
for Partial-Depth Repair of Concrete Pavements. Ames,
IA: National Concrete Pavement Technology Center,
Iowa State University.
Harrington, D., et al. 2008. Guide to Concrete Overlays–
Sustainable Solutions for Resurfacing and Rehabilitating
Existing Pavements, 2 nd Ed. Ames, IA: National Concrete
Pavement Technology Center, Iowa State University.
(www.cptechcenter.org/publications/overlays/
guide_concrete_overlays_2nd_ed.pdf.; accessed
August 5, 2011)
International Grooving and Grinding Association
(IGGA). ND. Buried Treasure: Discover Value With CPR.
West Coxsackie, NY: IGGA.
IGGA. 2010. Dowel Bar Retrofit Effective for CPR. West
Coxsackie, NY: IGGA.
Rasmussen, R., and S. Garber. 2009. Nonwoven Geotextile
Interlayers for Separating Cementitious Pavement Layers:
German Practice and U.S. Field Trials. Washington,
D.C.: FHWA. (http://international.fhwa.dot.gov/pubs/
geotextile/geotextile.pdf; accessed August 17, 2011)
Smith, K.D., T.E. Hoerner, and D.G. Peshkin. 2008.
Concrete Pavement Preservation Workshop–Reference
Manual. Washington, D.C.: FHWA. (www.cptechcenter.org/publications/preservation_reference_manual.
pdf; accessed August 5, 2011)
Stubstad, R., M. Darter, C. Rao, T. Pyle, and W. Tabet.
2005. The Effectiveness of Diamond Grinding Concrete
Pavements in California. Final Report. Sacramento, CA:
California Department of Transportation.
Van Dam, T., and P. Taylor. 2009. Building Sustainable
Pavements With Concrete. Ames, IA: National Concrete
Pavement Technology Center, Iowa State University.
(www.cproadmap.org/publications/sustainability_briefing.pdf;
accessed Dec. 5, 2011)
Van Dam, T., J. Meijer, P. Ram, K. Smith, and J.
Belcher. 2011. “Consideration of Economic and Environmental
Factors Over the Concrete Pavement Life
Cycle–A Michigan Study.” Proceeding of the International
Concrete Sustainability Conference. Boston, MA.
Zimmerman, K.A., and A.S. Wolters. 2003. Pavement
Preservation: Integrating Pavement Preservation Practices
and Pavement Management. Reference Manual, NHI
Course 131104. Arlington, VA: National Highway
Institute.
66 Ch. 7. CONCRETE PAVEMENT RENEWAL Sustainable Concrete Pavements A Manual of Practice

Chapter 8
END OF LIFE RECYCLING CONCEPTS
AND STRATEGIES
David Gress
The ultimate goal of recycling is to achieve a zero
waste stream target utilizing all byproduct materials
encountered in the rehabilitation or reconstruction of
a concrete pavement. Not only is this economically
advantageous but in addition local recycling minimizes
environmental impact by reducing the carbon footprint,
embodied energy, and emissions and enhances
social good by reducing the need for landfills and the
extraction of nonrenewable raw materials. Achieving
this goal ensures that a balance is struck among the
economic, environmental, and social factors that are
considered in the construction of concrete pavements.
As discussed in Chapter 2, the concept of recycling
must be viewed as a cradle-to-cradle undertaking as
opposed to past thinking of cradle to grave. There is no
practical grave for materials used in modern sustainable
infrastructure, only a new beginning which allows
application of current technologies to achieve the goal
of zero waste in the rehabilitation and reconstruction
of concrete pavements.
Driven by cost, need, limited resources, and an environmental
awareness of the benefits of sustainability,
concrete pavement recycling technology continues to
advance. In the past, economic cost was the driving
force that encouraged recycling, yet this is beginning
to change. Although cost will remain an important
driver, the social and political awareness of the need
to be sustainable has recently become more significant.
This is especially true in regions of high population
density where limited availability of construction
materials very often leads to cost-effective options for
recycling concrete pavements into new recycled concrete
and unbound base material. In addition, land-use
sensitivities, traffic considerations, as well as overall
cost are also of greater importance in urban areas. The
benefits of recycling include the following:
• Economic savings
• Reduced use of limited nonrenewable raw materials
• Decreased demand for fuel and associated emissions
from transport of waste to landfill and of new
materials to the site
• Improved land use, by minimizing both the need
for landfills and the need to develop more land for
resource extraction
Sustainable Concrete Pavements A Manual of Practice Ch. 8. END OF LIFE RECYCLING CONCEPTS AND STRATEGIES 67

1. Introduction to Recycled
Concrete
A subtle but important benefit of recycling concrete is
the potential benefit of reducing atmospheric carbon
dioxide (CO 2 ) through carbon sequestration. The paste
of the original concrete has approximately 25 percent
free calcium hydroxide (CH) which is potentially
capable of sequestering a significant amount of the carbon
dioxide that was initially released during cement
manufacturing due to the calcination of the limestone
(calcium carbonate). Sequestration is simply the process
of reversing the calcination that occurred in the
kiln when atmospheric CO 2 reacts with CH present
in the hardened concrete to form calcium carbonate
(CaCO 3 ). The rate of sequestration varies directly
with temperature, surface area, relative humidity, and
concentration of CO 2 . Work through the Recycled
Materials Resource Center (RMRC) at the University
of New Hampshire has shown the potential benefit of
sequestering carbon dioxide using the free CH found
in recycled concrete aggregate (RCA).
Sequestering is more efficient when RCA is used as
base material due to favorable environmental conditions
in a pavement subsurface base system as compared
to concrete exposed during normal service
which carbonates slowly due to minimum exposed
surface area, low moisture contents, and low matrix
permeability (Gardner 2007). When concrete is
crushed the resulting RCA has increased surface area
exposing more CH to the atmosphere which accelerates
the rate of carbonation (Haselbach and Ma 2008).
Even though concrete recycling is a proven technology,
it is not uncommon for the public as well as some
governmental agencies to discredit its benefits due to
a perception that the concrete is a waste material and
therefore of little use. Overcoming this requires a positive
attitude among the various stakeholders including
the responsible transportation agency, the environmental
agency in control, contractors, producers, and
the public. Success requires a common understanding
that recycled concrete is not a waste product and that
concrete has added value after it has been removed
and processed. To be successfully utilized, recycled
concrete must be viewed as another source of aggregate
with characteristics and value equivalent to the
aggregate material it replaces ton for ton.
Additional information on the use of recycled concrete
in transportation infrastructure can be found in the
following resources:
• FHWA (1997)
• FHWA (2007)
• AASHTO M 319, Reclaimed Concrete Aggregate for
Unbound Soil-Aggregate Base Course
• AASHTO MP 16, Reclaimed Concrete Aggregate for
Use as Coarse Aggregate in Hydraulic Cement Concrete
• ACPA Engineering Bulletin 043P, Recycling Concrete
Pavements
2. RCA Properties
It is important for users to understand the physical,
chemical, and mechanistic properties of RCA in relation
to its proposed uses. In general, hydraulic cement
concrete can easily be processed into RCA, which
has added value as an aggregate replacement in new
concrete, as a dense graded base material, as drainable
base material, or as fine aggregate; see Figure 8.1.
These RCA materials are recognized by ASTM and
AASHTO as viable aggregates, and there is no need to
request or apply for exceptions to standard specifications
when they are utilized as new aggregate substitutes.
Generally speaking, normal test criteria and
specifications that apply for conventional aggregate
also apply for RCA materials.
Figure 8.1 Recycled concrete aggregate (RCA)
(photo courtesy of Jim Grove, FHWA)
68 Ch. 8. END OF LIFE RECYCLING CONCEPTS AND STRATEGIES Sustainable Concrete Pavements A Manual of Practice

Thorough discussions of the typical properties of RCA
are found elsewhere (FHWA 2007, ACPA 2009, Obla
et al. 2007).
Physical Properties
RCA is an engineered processed material that has
properties dependent on its proposed use. For
instance, if its proposed use is an aggregate in concrete
then RCA must be processed to a higher standard than
if it were to be used as unbound, stabilized or drainable
base.
RCA is processed to meet the same application criteria
as required of any new aggregate. Although RCA must
pass the same testing requirements, it has unique characteristics
which vary from conventional aggregate.
For instance RCA consists of a combination of original
aggregate and old mortar and is very angular with
superior properties when used as a base material. The
quality of RCA concrete depends on the amount of
mortar that remains attached to the original aggregate.
If processing is such that little mortar remains and no
fines smaller than #4 sieve are used, the properties of
the RCA will be similar to the properties of the original
aggregate. On the other hand, if significant mortar
remains and excessive fines are used, the properties
of the RCA will significantly impact those of the new
concrete, compromising its performance compared
to concrete made with the original aggregates. This
uniqueness must be accounted for so that the RCA can
be used to its best value application. Essentially any
grading can be achieved by varying processing procedures
such as type of crusher.
The added quality value of RCA varies depending on
the application requirements of its use:
• RCA concrete: highest added value
• Drainable base: high added value
• Unbound base: intermediate added value
• Stabilized base: lowest added value
One of the major differences between RCA and conventional
aggregate is the absorption capacity due to
the presence of the mortar fraction on the recycled
particles. Absorption increases inversely with particle
size, and thus substitution of fine aggregate with RCA
at a rate in excess of 30 percent can result in decreased
concrete strength and the development of undesirable
finishing issues.
Although normally not problematic, the abrasion resistance
of RCA, as determined by the Los Angeles Abrasion
(LAB) test, is often reduced due to the presence of
the mortar fraction. The presence of materials-related
distress in concrete that is to be recycled, such as ASR
and D-cracking, has no effect on the RCA unless it is
to be used as aggregate in new concrete. The potential
for future D-cracking in the new concrete can be
mitigated by reducing the maximum size of the RCA
to ¾ in. or less. Similarly, ASR can be mitigated by
using normal mitigating techniques commonly used
for conventional concrete (AASHTO 2010, Gress et al.
2003 and 2005).
The mortar fraction of the RCA contains CH as a
byproduct of portland cement hydration which when
in the presence of water goes into solution. This solution
can react with atmospheric CO 2 and form a solid
material called tufa which in the presence of fines
can reduce the flow in improperly designed drainage
systems using RCA. Conditions which lead to this are
easily prevented in drainable bases (Wade et al. 1995).
Chemical Properties
The paste component of mortar adhering to the RCA
particles significantly influences the overall alkalinity
of RCA. The CH of a typical paving concrete is on the
order of about three percent by mass of the original
concrete. Calcium hydroxide in a saturated solution
(1.8 grams per liter at room temperature) creates a
basic pH of 12.4. Although this is a low solubility, the
CH is mobile through the pore system in the mortar
paste. Water draining through base material is thus
expected to have a basic pH above neutral caused
directly by the CH going into solution. A drainage base
effluent, except for unusually slow or stagnant flow or
the very first flushing of RCA with a high fines content,
will never be supersaturated, so the pH will be
significantly less than 12.4. Regardless, once the effluent
exits the drainage system, the pH will quickly be
reduced towards neutral by either dilution with water
or neutralization with soils and organics.
Sustainable Concrete Pavements A Manual of Practice Ch. 8. END OF LIFE RECYCLING CONCEPTS AND STRATEGIES 69

RCA produced from concrete located in the northern
tier of the United States may contain high levels of
chloride from the use of deicers which could cause
corrosion of steel reinforcement when used in CRCP
and JRCP applications. This can be mitigated through
the use of noncorrosive steel, steel with a corrosion
resistant coating, and/or corrosion inhibitors, and by
washing the RCA prior to use in concrete.
RCA that is obtained from a concrete source that has
been affected by ASR must be evaluated for remaining
expansion potential if it is to be used as an aggregate
substitute in new concrete and proper mitigation strategies
employed if expansion potential still exists. ASR
is not an issue if the RCA is to be used in unbound
layers including drainable base, dense-graded bases,
subbase, or fill material (Saeed et al. 2006).
Mechanical Properties
The mechanical properties of RCA are a function of
the quality and size of the particles. This is the direct
result of the effect of the mortar fraction which is
inversely related to the fineness. Generally the coarse
fractions have the least mortar so the properties of
particles larger than a #4 sieve (4.75 mm) have properties
similar to the original aggregate whereas the fines
have inferior properties compared to the original fine
aggregate. Generally RCA can be processed to have
more than adequate values of abrasion resistance,
soundness, and bearing strength.
3. RCA used in Concrete
State agencies have utilized RCA as aggregate in
concrete pavements with well documented field performance,
and surveys have been completed on the
original RCA concrete pavements to validate their performances
(Wade et al. 1995, Gress et al. 2009). The
results of these field investigations indicate that it is
possible to produce pavements from recycled hydraulic
cement concrete that are equivalent in all aspects to
pavements made with conventional aggregates. These
pavements were shown to be performing just as well
as their controls after 18 to 26 years of traffic (Gress et
al. 2009). However, a survey conducted by the FHWA
in 2004 when several states were visited to discuss
their current recycling procedures confirmed that 100
percent of the concrete pavements that were being
replaced were recycled into unbound base and drainage
material rather than RCA concrete.
Properties of Plastic RCA Concrete
The higher porosity and rough surface texture of RCA
has an effect on the plastic properties of new concrete.
The extent of the effect is a function of the mortar
fraction adhering to the RCA particles as well as the
angularity of the particles. Generally, as the amount of
mortar increases the effect on workability and finishability
can become problematic. Limiting the amount
of fines, which contain most of the old paste fraction,
to 25 percent minimizes water demand increase
(slump constant) by approximately 15 percent (Buck
1973, Mukai et al. 1973). The effect of harshness is
easily controlled at the maximum level of substitution
(30 percent) with the use of supplementary cementitious
materials (SCMs) and water-reducing admixtures.
When used in concrete RCA has the tendency to absorb
water and reduce slump as discussed above. The impact
of this is easily controlled by applying the same fundamental
pre-batching procedures successfully used with
lightweight concrete. This is recommended instead of
adding additional water during mixing.
Entrained air is not affected by RCA; however, the ability
to entrap high amounts of air due to the angularity
and rough surface area of the RCA makes it necessary
to increase the total amount of air by approximately
one percent to assure a good air-void system is developed
(Vandenbossche and Snyder 1993).
The measurement of air content with a normal pressure
meter is problematic unless it is specially calibrated
for the RCA being used due to the compressible
air in the voids within the old paste fraction of
the mortar (Fick 2008). Use of a volumetric method
of determining air content (Roll-a-Meter or air-void
analyzer) avoids the potential issues of measuring air
within the RCA in plastic concrete.
Properties of Hardened RCA Concrete
The physical properties of RCA can be engineered to
achieve properties in new concrete similar to, or even
better than, the original concrete. This is accomplished
70 Ch. 8. END OF LIFE RECYCLING CONCEPTS AND STRATEGIES Sustainable Concrete Pavements A Manual of Practice

by taking into consideration the properties of the
original mortar, the original aggregate, RCA grading,
substitution amount, and use of SCMs and admixtures.
Concrete containing RCA is easily engineered to satisfy
the design of any pavement by applying basic concrete
technology to specify a given mix design.
• Strength – The strength of RCA concrete can be easily
engineered to be less than, equivalent to, or even
superior to the original concrete made with natural
aggregates. The primary influence is the amount of
RCA fines (material passing the #4 sieve) that are
used in the mix design. Strength generally decreases
with increased fines; however, each mix is unique
with respect to the optimum amount of fines. In
general, if the substitution of RCA fines is restricted
to less than approximately 25 percent, the strength
of the RCA concrete will be similar to that of new
concrete made with natural aggregate. Higher substitution
of RCA lowers the strength. When admixtures
and SCMs are not utilized to enhance RCA
concrete, strength can be reduced as much as 24
percent when only coarse RCA is used and as much
as 40 percent when both coarse and high amounts
of RCA fines are utilized (Hansen 1986). These
reductions have been shown to be the direct result
of the mortar content of the RCA (Snyder 1994).
• Modulus of elasticity – Like strength, the static
modulus of elasticity of RCA concrete is also
inversely related to the RCA mortar content and
the mix design of the new concrete. When admixtures
are not utilized to enhance the new concrete,
the elastic modulus can be reduced as much as 30
percent when only coarse RCA is used, and up to
40 percent when both coarse and high amounts of
RCA fines are utilized (ACI 1994).
• Relative density – The relative density of RCA concrete
is up to 15 percent lower due to the lighter
weight mortar fraction than concrete manufactured
using natural aggregate (Hansen 1986). An
advantage of reduced relative density is the inflated
volume relative to the weight of the RCA concrete
allowing more concrete to be produced than
removed from a given recycling project.
• Volumetric stability – The wetting and drying shrinkage
of RCA concrete is also directly affected by
the mortar content. Aggregates with lower elastic
moduli experience higher wetting and drying strain
due to significantly less restraint when the new and
old paste wets and dries. Concrete can be expected
to have 20 to 50 percent higher wetting and drying
shrinkage when it contains coarse RCA and natural
sand, and 70 to 100 higher shrinkage when it
contains both coarse and fine RCA (ACI 1994).
Higher moisture sensitivity requires more detailed
consideration of joint design in JPCP than would be
necessary in normal concrete.
The coefficient of thermal expansion of concrete
made with RCA is approximately 10 percent higher
than the original concrete made from any specific
aggregate, but in some cases may be as much as
30 percent higher. And, as with wetting and drying,
temperature induced strains merit more detail
in establishing joint spacing to alleviate potential
warping and curling stresses in pavements.
Creep of RCA concrete, typically 30 to 60 percent
higher than concrete containing natural aggregates,
is also increased due to higher paste content.
Designing for the effect of creep is similar to what
is done with lightweight aggregate concrete (ACI
1994).
• Permeability – The permeability of concrete made
with RCA is highly affected by the water-tocementitious
material (w/cm) ratios of both the
original and new concrete. The old paste adhered to
the RCA particles creates a short circuit for movement
of water through RCA concrete if the new
w/cm ratio is less than the original. The ability of
water to be transported through RCA concrete can
be engineered to be less than, equal to, or greater
than the original concrete by varying the w/cm ratio
of the concrete containing RCA, resulting in permeability
ranging from less than to more than 500
percent greater than the original concrete.
• Durability – The durability of RCA concrete is
not significantly different from that of the source
concrete. Freezing and thawing resistance, for
instance, is not an issue with RCA concrete providing
the new paste contains an adequate air-void
size distribution. The issue is more in evaluating
the air content as discussed in the plastic concrete
section. D-cracking, a special case of freeze-thaw
distress, has been shown to be improved when the
Sustainable Concrete Pavements A Manual of Practice Ch. 8. END OF LIFE RECYCLING CONCEPTS AND STRATEGIES 71

maximum size of the RCA particles is restricted to
less than the critical size to cause D-cracking (Sturtevant
2007, Gress et al. 2009).
• Alkali-silica reactivity – Concrete containing RCA
may have potential for ASR if the source concrete
contained alkali-reactive aggregate. It cannot be
assumed that ASR will not develop in the new concrete
if special control measures are not taken. If the
RCA contains reactive aggregate, mitigation strategies
must be developed, even if expansive ASR did
not develop in the original concrete. Petrographic
examination and remaining ASR potential expansion
tests are recommended to make this judgment
(Stark 1996, Gress et al. 2000a and b, FWHA 2009).
Severely ASR-damaged concrete has been successfully
recycled into new concrete with little evidence
of recurrent ASR damage (Gress et al. 2009). If SCM
is used as a means to mitigate ASR in RCA concrete,
the appropriate dosage levels should be determined
by using ASTM C 1567. Other mitigating techniques
include admixtures such as lithium nitrate
and low alkali cement.
• Carbonation and corrosion – Research indicates that
rates of carbonation of concrete containing RCA
is up to 65 percent higher than that of concrete
containing only natural aggregate (Gardner 2007).
From a sustainability view, reducing atmospheric
CO 2 through carbonation is very beneficial; however,
for reinforced structures, increased carbonation
can cause more rapid corrosion of embedded
steel reinforcing if the carbonation front reaches the
depth of the steel, particularly in locations where
chloride concentrations are high. These rates and
depths of carbonation significantly decrease with
reduced w/cm ratios (Rasheeduzzafar and Khan
1984).
4. RCA in Foundations
RCA has several applications as support material.
RCA as Unbound Base Material
Recycling concrete pavements into RCA is a viable
alternative for unbound base course construction.
RCA as a rule is considered a superior material for
unbound applications such as bases when compared to
conventional new aggregate; however, RCA may have
higher value for use in other sustainable applications
such as replacing natural aggregate in new concrete.
From an environmental perspective, the use of RCA
as unbound base material has very significant benefits
including lowering CO 2 emissions, reducing transportation
fuel consumption, lessening the use of higher
valued natural aggregate, and sequestering of CO 2
through carbonation of the CH within the increased
surface area of the RCA particles.
While it is estimated that 100 percent of replaced
concrete pavements are recycled, approximately 70
percent of all state agencies utilize RCA as unbound
base course (RMRC Survey 2011). RCA has similar
or better properties than natural aggregate that are
essential for high-quality base course construction.
For instance RCA has rougher surface texture, higher
shear strength, higher rutting resistance, and higher
resilient modulus. These exceptional qualities allow
for unrestricted use of RCA as base materials up to and
including 100 percent substitution of new aggregate.
Environmental evaluation is not necessary when RCA
is used for base, subbase, and subgrade improvement.
Pavements with a materials-related distress such as
ASR, D-cracking, or freeze-thaw distress can be effectively
used as unbound base material without concern
of reduced performance. The only exception, although
rare, is that in areas where an external source of sulfate
is present, RCA should be utilized with great caution
(Saeed et al. 2006). In such areas where exposure to
sulfate is possible from subgrade soils, ground water,
or other external sources, the existing concrete must
be extensively evaluated for expansion resulting from
ettringite formation.
It is generally accepted that after unbound RCA base
is compacted, its strength and stiffness increase. A
misinterpretation of this phenomenon is that this is
due to hydration of unhydrated portland cement contained
within the paste portion of the RCA. Instead,
the increased stiffness is credited to the carbonation
of very soluble CH released by the RCA in the presence
of moisture, which is constantly available in the
subsurface base.
Testing criteria for RCA are similar to those required
for natural aggregate; typically, this is a non-issue for
RCA derived from concrete utilized in pavements. One
72 Ch. 8. END OF LIFE RECYCLING CONCEPTS AND STRATEGIES Sustainable Concrete Pavements A Manual of Practice

exception is the sulfate soundness test (ASTM C 88)
which destroys the RCA paste fraction due to sulfate
attack. This test should not be specified for evaluating
RCA as it has no relevance to the performance of
RCA as an unbound base material. It is also sometimes
difficult to pass the aggressiveness of the LAB hardness
test if the concrete was made with marginal aggregate
and/or when the RCA paste content is high. To address
these two exceptions in RCA specifications, it is common
to eliminate the sulfate soundness testing and
increase the LAB limit to 50 percent.
The number-one benefit of using RCA as base material
is the economic savings resulting from lower transportation
costs, elimination of landfill charges to dispose
of the removed concrete, and the savings derived from
not buying natural aggregate base material. The use of
RCA varies state by state but is typically a contractor
decision in that it is not usually specified except as an
option. More moisture is required during construction,
but compaction is easier to obtain than with natural
aggregate. As with all aggregates, control of grading
and segregation needs to be given proper attention
during base construction.
It is also possible to effectively utilize the existing pavement
as base by employing fractured-slab techniques,
thus leaving the concrete in place. Several fracturedslab
techniques can be used including rubblization
and crack and seat. As these two techniques are done
in place, no trucking, crushing, or aggregate grading
is required and thus costs are lowered. Newer in-situ
recycling techniques have been deployed on a number
of projects that actually go a step further than fractured-slab
techniques by actually lifting the concrete
off grade, crushing it, and placing it back on grade
ready for compaction. The mobile crushers are track
mounted, and the entire operation moves along the
alignment requiring no additional trucking. Some of
these in-situ recycling methods even size the aggregate
to further improve performance.
To achieve a more conventional unbound base, it is
necessary for the concrete pavement to be fractured,
removed from the site, and crushed using conventional
crushing equipment. The crusher is often
sited near the pavement to reduce transportation
costs and impacts. The equipment can be simple or
sophisticated. The crushed material is processed and
transported to its designated location for spreading
and compaction. In a properly tuned crusher it is
possible to return 100 percent of the crushed material
as unbound base. Adding additional lanes during
reconstruction easily consumes the inflated volume of
base material produced, whereas if there are elevation
control issues and no new lanes then it may be difficult
to use 100 percent of the RCA on site.
RCA as Drainable Base
When RCA is used as a drainable base, special consideration
must be given to the design. A proper design
places all RCA below the elevation of the inlet of the
drainage system and, if geotextiles are used, the flow
must be parallel to the geotextile and not through it.
Improper design will result in the formation of tufa
from the fines and CH, clogging pipes and other elements
of the drainage system.
Effluent from drainable bases containing RCA can
have pH values greater than 7.0 due to the leaching
of CH. This has not been found to be problematic in
ecosystems. Although effluent from an RCA drainable
base can have increased pH, especially during the first
flushing cycle of water, it has no buffering capacity and
is equivalent to adding lime to stabilize the effect of
acid rain on a lawn. As such, there is little to no environmental
impact. The ability of the CH to be removed
from the paste in the leachate is a function of paste
permeability which is extremely low, being on the
order of 10 -7 cm/sec. Nevertheless it must be expected
that CH will slowly go into solution and be removed
with flowing effluent. In stagnant flow conditions, the
leachate could reach a pH as high as 12.4; however,
this will quickly dissipate as the leachate encounters
soils and organic materials commonly present in soils.
In such cases, vegetation in the immediate vicinity of
drainage structures can be affected before neutralization
occurs.
RCA as Stabilized Base
RCA is easily stabilized as a base material by adding
cementitious binders (such as lime and fly ash (LFATB)
or portland cement (CTB)) or an asphaltic binder
(ATB). As was discussed for unbound bases, the high
angularity and rough surface texture of RCA makes
it an exceptional base material that in many ways is
superior to naturally available materials. When the
Sustainable Concrete Pavements A Manual of Practice Ch. 8. END OF LIFE RECYCLING CONCEPTS AND STRATEGIES 73

cementitious content is increased, a stronger material
called lean concrete base (LCB) is easily produced.
The use of RCA for these applications has added value
because 100 percent of the product can be utilized and
there is no need to remove the fine portion of the RCA
which, as discussed, is problematic for other applications.
Using RCA fines in stabilized base applications
has no negative impact on its physical or chemical
properties.
It is also possible to use RCA to create asphalt stabilized
bases (ATB). Conceptually the process is equivalent
to making CTB except the effect of absorption can
be problematic, not from a moisture control issue but
as an economic issue since there will be an increased
demand for asphaltic binder due to the absorption of
the RCA. The extra absorbed asphalt binder is, for all
practical purposes, unavailable for improving the base’s
physical properties.
5. Recycled Concrete in Other
Applications
Special applications of recycled concrete are limited
only by the imagination of the designer. For instance,
architectural use of large irregular fractured slabs can
result in the innovative use of recycled concrete ranging
in size from riprap to massive slabs. Likewise, use
of reclaimed rubble can be used as fill material, backfill
for retaining walls, pipe bedding, artificial reefs for fish
habitats, construction site soil stabilization, etc. (Vandenbossche
and Snyder 1993, CMRA 2011).
• RAP in concrete – Concrete can be made using
recycled asphalt pavement (RAP) as a portion of
the aggregate, using conventional concrete mixing
and construction practices. Concrete made with
RAP exhibits a systematic reduction in compression
and tension strengths and an increase in toughness.
Generally, strength declines and toughness increases
with increased amounts of RAP. The coarse particles
have the least effect on these properties, suggesting
that coarse RAP may be more practical to use as an
aggregate substitute (Huang et al. 2005).
• RCA in two-lift construction – As discussed in Chapter
3, two-lift concrete pavement design is re-establishing
itself in the United States and has the potential
of becoming the sustainable pavement of the
future. Two-lift pavement construction can be used
to satisfy the economic, environmental, and social
aspects essential for sustainable design. Economically
the benefits include reduced capital investment
and greatly increased service life with lower
maintenance and rehabilitation costs. Environmental
benefits include a smaller carbon footprint,
reduced expended energy, and less overall pollution
and waste. Societal aspects include reduced disruption,
noise reduction, and improved safety through
increased skid resistance.
The future of two-lift construction for sustainable
construction of concrete pavements is exceptional.
It is known that the cost and availability of superior
quality materials will continue to decline. The
use of RCA of any quality is more than adequate
for the construction of the thick underling bottom
lift of the two-lift system, including RCA mixed
with RAP. This reduces demand for the higher
quality, costly aggregate materials typically used in
the high-performance top lift. The result is a high
performance pavement, consisting of a thin wearresistant
surface bonded to a tough, low-modulus,
high fatigue-resistant, thick bottom lift, creating a
sustainable composite pavement. Even when the
pavement nears the end of its useful service life, the
high quality thin top layer can easily be selectively
reclaimed for reuse, thus ending the cycle of “cradle
to grave” and starting the new wave of the future,
“cradle to cradle”—a truly sustainable concept we
can live with.
6. References
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ACPA. 2009. Recycling Concrete Pavements. Engineering
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American Association of State Highway and Transportation
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AASHTO. 1986. Standard Specification for Materials:
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Fick, G. J. 2008. Testing Guide for Implementing Concrete
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M. A., B. Fournier, and D. Durand. Alkali-Aggregate
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Gupta, J. D., and W. A. Kneller. 1993. Precipitate Potential
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OH-94/004. Ohio Department of Transportation.
Gupta, J. D., W. A. Kneller, R. Tamirisa, and E.
Skrzypczak-Jankun. 1994. “Characterization of Base
and Subbase Iron and Steel Slag Aggregates Causing
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Bituminous and Concrete Materials in Granular
Base and Earth. Report MI-137. Downsview, Ontario:
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Hansen, T.C. 1986. “Recycled Aggregates and Recycled
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Huang, B., X. Shu, and G. Li. 2005. “Laboratory
investigation of portland cement concrete containing
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(IGGA). 1990. Grinding Slurry Analysis. International
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for Aggregate of Concrete.” Proceedings of the Seminar
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Obla, K., H. Kim, and C. Lobo. 2007. Crushed
Returned Concrete as Aggregates for New Concrete. Final
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A Source of New Aggregate.” Cement, Concrete,
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Poole. 2006. Evaluation, Design and Construction Techniques
for Airfield Concrete Pavement Used as Recycled
Material for Base. Final Report, IPRF-01-G-002-03-5.
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and Foundation Stiffness on the Deterioration of
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from Concrete Exhibiting Alkali-Silica Reactivity.
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76 Ch. 8. END OF LIFE RECYCLING CONCEPTS AND STRATEGIES Sustainable Concrete Pavements A Manual of Practice

Chapter 9
CONCRETE PAVEMENTS IN THE
URBAN ENVIRONMENT
Tom Van Dam
Emily Lorenz
According to the 2010 U.S. census, 83.7 percent of the
308.7 million inhabitants of the United States reside
in metropolitan areas, living in core urban areas with
a population of 50,000 or more (Mackun and Wilson
2011). The number of people living in urban and suburban
areas is increasing while fewer are in rural areas,
resulting in increased population density. Increasing
density has both beneficial and detrimental effects with
respect to the transportation industry. High population
density means that distances traveled within the
city are low (reduction in average trip distance), thus
reducing fuel consumption, but it also means that
considerable resources must be transported into the
city, with the associated traffic and emission impacts.
Cities are often surrounded by suburban sprawl, which
has a highly adverse impact due to large commuting
distances that are economically, socially, and environmentally
costly, especially when traffic is delayed due
to road maintenance. The infrastructure needs of a city
are significant, including pavements, sidewalks, water,
sewer utilities, and power transmission lines. Such
systems are extremely sensitive to disruption, resulting
in large social impacts when natural or manmade
disasters occur.
Pavements represent a key element in this infrastructure,
and it is estimated that paved surfaces for travel
and parking can account for 29 to 39 percent of the
land surface area in urban regions (Akbari et al. 1999,
Rose et al. 2003). The importance of incorporating
sustainability measures into the pavement life cycle is
thus amplified, as environmental and societal impacts
of the built environment are concentrated in urban
environments. Traffic congestion and user delays,
smog, safety concerns, and even aesthetics play a
greater role in design because any impact has the
ability to affect a larger population. Thus, potential
strategies that may be cost prohibitive in a rural location
may now become cost effective. Also, strategies
that would not have been considered before are now
applicable when the societal impacts are considered.
Concrete pavements provide unique characteristics
that make them useful in an urban environment. Of
specific interest in the urban environment is their
longevity, which reduces interruptions (and the associated
traffic impacts) for rehabilitation. Also of interest
is the high surface reflectivity index (SRI) as discussed
in Chapter 6. High SRI can help mitigate the urban
heat island effect while also decreasing the need for
and cost of artificial lighting (Marceau and VanGeem
2007). In addition, the use of photocatalytic cements
and coatings can be applied in the urban environment
to provide additional reflectivity while also converting
NO x , SO x , and volatile organic compounds into
solids that precipitate out and can be washed off the
pavement.
Concrete can also be colored and molded to create
aesthetically pleasing pavement landscaping designs
that can be constructed at crosswalks or busy intersections
to help slow the flow of traffic in urban neighborhoods,
making them more pedestrian friendly.
Additionally, concrete pavements can be effectively
textured to help reduce pavement-tire noise that could
otherwise detract from an otherwise quiet neighborhood.
Finally, pervious concrete can be constructed
in urban settings to help address critical surface storm
water run-off issues.

1. The Urban Environment
A sustainable-growth strategy is to build in already
densely populated areas with the goal of improving
or rehabilitating existing dense zones. Undeveloped
land is becoming scarce, and consumption of land
for pavements, bridges, and buildings reduces the
amount of land that would be otherwise available for
agriculture, wildlife habitats, and parks. With any
development, it is critical to implement sustainable
site-development strategies by minimizing disturbance
to existing ecosystems, restoring areas damaged
during construction, and designing pavements,
bridges, drainage systems and buildings to minimize
their environmental impact. As structures are rehabilitated
in urban centers, there is opportunity to add
resources such as bike paths and walkways, further
increasing livability and potentially reducing traffic.
Compared to rural areas, urban areas are more suitable
for walking and pedestrian traffic as businesses
(employers) and services (such as basic utilities,
schools, banks, and hospitals) are in place (Loehr
2009) and distances traveled are much shorter. Further,
larger metropolitan areas typically have alternative
forms of transportation available, such as commuter
trains, trams, light rail, and public buses that
reduce the demand for automobile travel.
All of these attributes make cities desirable places to
live, as well as more sustainable. But it also makes
cities more sensitive to changes in the environment.
For instance, even small disruptions to traffic flow
due to construction affect many more people than
in rural areas. Thus, pavement design strategies to
extend design life and reduce the need for closures
are extremely important in the urban environment.
2. Reducing Environmental
Impacts in the Urban
Environment
Concrete pavements can be part of the solution in
mitigating the environmental impacts of dense urban
environments.
Light, Reflective Surfaces
Concrete pavements can help reduce the urban heat
island effect and the reliance on artificial lighting.
Urban Heat Island Effect
The heat island effect occurs where a local area of elevated
temperature is located within a region of relatively
cooler temperatures, as discussed in Chapter 6. Because
of the greater density of paved and covered surfaces in
urban environments, the heat island effect occurs most
frequently in urban areas. The effects of urban heat
islands are broad, resulting not only in increased levels
of discomfort and increased energy to artificially manage
temperature within buildings but also, occasionally, in
life-threatening conditions (FEMA 2007). These lifethreatening
conditions can develop when temperatures
rise above 75˚F, which increases the probability of formation
of ground-level ozone (commonly called smog) that
exacerbates respiratory conditions such as asthma. At
the same time, higher temperatures also lead to greater
reliance on air conditioning, which leads to more energy
use.
Mitigating the urban heat island effect is a priority
for groups such as the U.S. Environmental Protection
Agency (EPA), which suggests using reflective paving
materials, such as conventional concrete, as one mitigation
strategy (EPA 2009). Additives that can further
increase the SRI of concrete, such as slag cement or
light-colored fly ash, are also recommended (Van Dam
and Taylor 2009).
Artificial Lighting
There are additional benefits in using light-colored
concrete pavements. As Wathne (2011) discusses, lightcolored
pavements can also improve safety by improving
night visibility while reducing artificial lighting requirements,
thus saving energy and reducing emissions. Gajda
and Van Geem (2001) showed that concrete pavements
require fewer lights per length of roadway than dark-colored
pavements to achieve the same illumination level.
In a similar study, Adrian and Jabanputra (2005)
researched the influence of pavement reflectance on
lighting requirements for parking lots. In their study,
they compared asphalt and concrete surfaced roadways
in four ways:
• Total light reflected from a surface
• Relationship of surface reflection characteristics and
power distribution of lighting lamps
• Luminance and visibility levels with typical parking
lot lighting systems
78 Ch. 9. CONCRETE PAVEMENTS IN THE URBAN ENVIRONMENT Sustainable Concrete Pavements A Manual of Practice

• Equivalent luminance of two systems based on varying
lamp wattage and number of fixtures
Results of their research show that, on average, a lighter
surface is 1.77 times more luminous than a darker surface
and has a more uniform luminance distribution.
An analysis was also performed to create equivalent
luminance levels for the two systems based on varying
the number and intensity of the luminaires being used
to establish the relative energy use of the two systems.
When varying the lamp power and assuming that the
parking lot lights are on for five hours a day, the darker
parking lot used 60 percent more energy than the
lighter parking lot. With modifications to the number
of poles needed and still assuming that the parking lot
lights are on for five hours a day, the darker parking lot
used 57 percent more energy than the lighter parking lot.
In urban environments, photocatalytic cements and/or
coatings may be a viable option to help maintain highly
reflective surfaces. Although photocatalysts, such as the
anatase form of titanium dioxide, have been known for
decades to have the ability to keep surfaces clean, they
have recently been gaining attention for urban infrastructure
applications by incorporating it in cement
(Italcementi 2005). The use of a photocatalytic titanium
dioxide cement for the Gateway concrete sculptures
placed at either end of the reconstructed I-35W bridge
in Minneapolis in 2008 (ACI 2009) was one early U.S.
application of this technology, but since then it has
been used in interlocking concrete pavers (Schaffer
2009) and in two-lift concrete pavement construction
(Gates 2011). A white photocatalytic material such as
titanium dioxide is not only highly reflective at the time
of construction, it is self-cleaning and maintains its high
solar reflectance and greater visibility for a longer time.
On the other hand, the material is more expensive than
normal portland cement, requiring a balance between
increased costs and reduced environmental impact.
bridge piers contained 15 percent portland cement, 18
percent fly ash, and 67 percent slag cement (ACI 2009).
This high-SCM-content concrete reduced the carbon
footprint and embodied energy of the concrete by
approximately 75 percent (Van Dam and Taylor 2009).
As discussed in Chapter 6, the energy consumed during
pavement use through vehicle-pavement interaction
may have a significant impact on the life-cycle energy
use of the pavement. This has greater relevancy in
urban areas where greater traffic volume dictates that
even a minor reduction in fuel consumption and corresponding
reduction in emissions for a given pavement
will result in an improvement in sustainability.
In addition, vehicle emissions can also be “treated” as
they interact with photocatalytic surfaces while exposed
to sunlight. This has been demonstrated through
laboratory experiments and in-service structures and
pavements that have been constructed and monitored
to determine the applicability of photocatalytic cements
and coatings as a way to reduce air pollution, including
NO x , SO x , and VOCs (TX Active ® 2011). Although this
technology is just catching on in the United States, concrete
pavers surfaced with photocatalytic titanium dioxide
are being marketed in urban areas throughout the
country and the world. Figure 9.1 shows an example
from Japan where photocatalytic concrete pavers have
been used to create an aesthetically pleasing sidewalk
while also reducing air pollution. As the effectiveness
of photocatalytic cements and coatings continues to be
demonstrated, their use is expected to grow in the urban
environment.
Reduced Emissions, Enhanced Fuel
Efficiency
As discussed in Chapter 4, one way to reduce the
embodied emissions in concrete pavements is to use
high supplementary cementitious material (SCM)­
content binder systems and/or those containing portland-limestone
cements. One such system was used in
elements of the I-35W Bridge reconstruction project
in Minneapolis, in which the binder for the concrete
Figure 9.1 Photocatalytically active colored
concrete pavers in Japan (Chusid 2005)
Sustainable Concrete Pavements A Manual of Practice Ch. 9. CONCRETE PAVEMENTS IN THE URBAN ENVIRONMENT 79

Reduced Waste
There are only a finite number of areas available for landfilling
of waste, and these areas are becoming increasingly
scarce in densely populated urban areas. Typically, urban
areas must dispose of waste at a landfill outside of the
city or metropolitan area limits. As an example, New York
City (NYC) transported over 3,000,000 tons of municipal
solid waste in 2004 over great distances to other states
such as Pennsylvania, Virginia, and Ohio (Lauber et al.
2006). This not only incurs a high economic cost but
also generates significant environmental costs due to
increased energy usage and emissions.
One way of reducing the amount of waste is to make use
of the existing pavement materials. For example, innovative
in-situ recycling techniques—such as recycling
trains that can recycle existing pavements in place—have
recently been employed on existing concrete pavements
(Van Dam and Taylor 2009). These techniques reduce
costs and the environmental impacts of transportation by
reducing the amount of solid waste that must be transported
either to crushing plants or landfills while reducing
the amount of virgin materials needed on site (see
Chapter 8).
of water per minute per square foot of surface, as
illustrated in Figure 9.3. This allows rainwater to seep
into the ground versus running off, thereby recharging
groundwater instead of rapidly moving from the
pavement surface to nearby bodies of water. Surface
water with organic contaminants is also allowed to
percolate into the ground where it is filtered by the
underlying soil. Thus, previous concrete can be used
in urban areas to eliminate the need for other storm
water management devices such as retention ponds
and swales (PCA 2011).
It is important to recognize that—although the U.S.
EPA (2011) cites the use of pervious concrete as a
Best Management Practice (BMP) for the management
of storm water runoff on a regional and local
basis—pervious concrete is not applicable in all situations.
For example, pervious concrete is best used
in low-volume traffic applications such as roadway
Reduced Storm Water Run-off
Precipitation runs off hard, impermeable surfaces (such
as pavements) much faster than off undeveloped or
vegetated surfaces. The concern from the standpoint of
environmental impact is that storm water systems will
be overfilled when large areas of vegetation are replaced
with paved or hard surfaces, resulting not only in flooding
but also in erosion and the transport of pollution into
nearby surface waters and increased temperatures in the
streams. Typical storm water management techniques,
such as retention ponds, are expensive and difficult to
implement in urban areas due to lack of available land.
Thus, innovative solutions are acutely needed for these
locations.
One innovative solution to address the storm water
quantity and quality control issue is the use of pervious
concrete (NRMCA 2009); see Figure 9.2. Pervious
concrete is manufactured in place with a substantial void
content—between 15 percent and 25 percent—created
by the use of little or no sand (Tennis et al. 2004).
With its high void content, pervious concrete allows rainwater
to drain through it at a rate of about 3 to 8 gallons
Figure 9.2 Pervious concrete (photo courtesy of
John Kevern, University of Missouri-Kansas City)
Figure 9.3 Water passing through pervious
concrete (NRMCA 2009)
80 Ch. 9. CONCRETE PAVEMENTS IN THE URBAN ENVIRONMENT Sustainable Concrete Pavements A Manual of Practice

shoulders, parking lots, or alleys. It is ideal for application
in urban areas where parking and alleys are a
common feature.
The Chicago Department of Transportation (CDOT)
has an effective program in which it is using pervious
concrete in many of the city’s alleys. Called the Green
Alley program, one of the initiatives is to use more
permeable pavements to divert storm water from
the sewer system. The city is thus saved significant
expense by not having to pump and treat storm water
that is co-mingled with sewage. Pervious concrete
pavements have been used in both center-trench and
full-width applications. CDOT (2010) launched the
Green Alley program because it could reap three sustainability
benefits simultaneously:
• Management of storm water
• Heat-island reduction because pervious surfaces
are cooler
• Use of recycled materials in the mixture
Ultimately, by integrating paving and drainage, less
site area is typically needed to manage storm water,
allowing a more compact site development footprint.
This is critical in an urban environment.
vehicle and pedestrian areas, for example). At the same
time, various texturing patterns can be achieved by
brushing and washing away surface mortar as the concrete
begins to harden, exposing the stone or gravel in
the concrete, or by embedding attractive stones such as
marble, granite chips, or pebbles into the surface.
Semi-hardened concrete can be pattern-stamped with
special tools to create the custom look and feel of slate,
cobblestone, brick, or tile. Figure 9.4 is a photograph
of a Blome Granitoid pavement constructed in 1906 in
Calumet, Michigan, in which the aesthetically-pleasing
brick pattern was also functional, preventing horses
from slipping. The patterns can help scale down large
expanses of paving, as shown in Figure 9.5.
Or, simply, concrete can be cast in a wide variety of
colors. Pastels and earth tones are produced by mixing
mineral pigments throughout the concrete. For deeper
3. Reducing Societal Impacts
in the Urban Environment
Concrete’s versatility makes it a good solution to create
highly functional, economical pavements that also
meet environmental and social needs (Van Dam and
Taylor 2009). By using concrete, pavement designers
can enhance communities, incorporating color and
texture into aesthetically pleasing patterns, demarcating
pedestrian crossings, quieting road noise, providing
safer surfaces, and reducing user delays.
Enhanced Aesthetics
Concrete is an extremely moldable material and can
be transformed to fit into its surroundings. Aesthetic
interest can be added to concrete elements with the
use of texture, color, or patterns. Although it is not
likely to be cost effective for the main riding surface
of a concrete pavement, cross walks, walk ways,
shoulders, and other elements of the pavement can
receive different treatments to add visual interest or
to demarcate one area of use from another (separating
Figure 9.4 Blome Granitoid concrete pavement
constructed in 1906 in Calumet, Michigan; the brick
pattern was stamped into the surface to keep horses
from slipping (photo courtesy of Tom Van Dam,
CTLGroup
Figure 9.5 Modern Blome Granitoid concrete
pavement (photo courtesy of Tom Van Dam,
CTLGroup)
Sustainable Concrete Pavements A Manual of Practice Ch. 9. CONCRETE PAVEMENTS IN THE URBAN ENVIRONMENT 81

tones, finishers use the dry-shake method—sprinkling
powdered, prepackaged color hardeners onto a freshly
cast concrete slab, then troweling it into the surface.
Aesthetically pleasing, durable pavements can be
achieved by using interlocking concrete pavers.
These can also be designed to be permeable, highly
reflective, and/or photocatalytic to meet a number of
sustainability goals. Interlocking pavements are ideal
in locations where there are underground services
because if repairs are needed in the utilities, the pavers
can be lifted and replaced with minimal impact.
Noise Mitigation
Noise from pavement construction or maintenance,
or noise generated through tire-pavement interaction,
should be considered in the quest for more
sustainable pavements, as it is known that elevated
noise levels can cause physiological and psychological
impairments in living creatures (Hogan 2010, Passchier-Vermeer
and Passchier 2000).
In urban environments, sound barriers are built to
protect surrounding communities from noise generated
by traffic, particularly on fast-moving expressways.
Yet, through care at the pavement design stage,
the need for such barriers may be eliminated if an
effective noise-mitigation solution, such as use of quieter
pavement surface textures, is employed.
Surface texture is desirable to increase friction and
enhance safety, yet it has been shown to have a
significant impact on noise generation through tirepavement
interaction (Rasmussen et al. 2007). The
relationship between noise and community disturbance
adjacent to roadways is not new, and pavement
engineers have invested considerable effort to lessen
noise generated from the interaction of the tire with
the pavement surface.
Rasmussen et al. (2008) conducted research to identify
factors contributing to the objectionable noise
and developed pavement-noise mitigation strategies
that result in safe and quiet concrete riding surfaces.
Specifications have been developed (Rasmussen et al.
2011) to reduce tire-pavement noise, including the
use of drag-textured or longitudinally tined surfaces
(Figure 9.6) and diamond grinding including the Next
Generation Concrete Surface.
However, the same communities that object to noise
generated on a high-speed roadway may have a different
set of criteria for local, slow-speed roads serving their
neighborhoods. At slower speeds (less than 35 mph)
engine noise is dominant; therefore, pavement texturing
will have little effect on noise. In such locations, noise
may less critical than aesthetics, pedestrian safety, high
reflectivity, or surface drainage. It is even possible that
an urban neighborhood might desire that “roughness” be
designed into the surface to produce a calming effect on
vehicles exceeding the speed limit and to create a more
livable community (Van Dam and Taylor 2009).
Health and Safety
The first concern of any transportation agency is to
provide roadways that are safe for the user and the community.
This means that, among many other factors, the
surface must provide adequate surface friction while
minimizing splash and spray, must not exhibit potentially
hazardous distresses (potholes, faulting, blowups), and
must provide enhanced night-time and poor-weather visibility
for the safety of drivers and pedestrians (Van Dam
and Taylor 2009).
As mentioned in Chapter 6, urban heat islands contribute
to lower quality local air and water quality, which can
be mitigated by the use of pavements with greater solar
reflectance, such as concrete.
Reduced User Delays
There is a reason that most major metropolitan radio
programs provide a traffic report every morning. Traffic
and delays due to traffic are huge financial, environmental,
and social issues in urban environments. Time
wasted due to congestion during maintenance and reconstruction
activities increases the stress of drivers, potentially
negatively impacting their health. Moreover, traffic
delays lead to an increase in user costs.
Figure 9.6 A potentially quiet surface (viewed from
the side)
82 Ch. 9. CONCRETE PAVEMENTS IN THE URBAN ENVIRONMENT Sustainable Concrete Pavements A Manual of Practice

Not only do traffic delays annoy users and contribute
to an increase in their costs and travel times, there is a
broader environmental impact as well. The surrounding
community and other populations are also affected
by delays, as idling vehicles consume fuel and generate
pollutants. Therefore, great benefit is derived from
concrete pavement systems that minimize delay over
the life cycle.
This can be accomplished through careful design
(Chapter 3) and construction (Chapter 5) that minimize
delay during the construction phase. This might
include consideration of precast concrete pavements or
other rapid construction methods. Maintaining good
pavements in good condition using maintenance strategies
that have minimal impact on operations is another
strategy to minimize traffic delays (Chapter 7). This can
be effectively achieved by performing periodic diamond
grinding operations on the pavement structure, which
maintains high levels of smoothness while incurring
reduced environmental costs and decreased user costs.
As a concrete pavement approaches the end of its structural
life, concrete overlays can be rapidly constructed
to restore structural capacity with far less traffic disruption
than reconstruction.
4. Summary
Concrete pavements are uniquely suited to enhance
sustainability in the urban environment. They are
naturally light in color, which helps mitigate the urban
heat island effect, increases night-time visibility for
enhanced safety, and allows the reduction of artificial
lighting while maintaining the same ambient light levels.
Moreover, concrete pavements can be colored and
textured to provide a quiet and safe surface under vehicle
operations or, for slower speed applications, can
be constructed to slow traffic through busy pedestrian
areas by channelizing. Pervious concrete pavements are
commonly used to address storm water runoff in the
urban environment, whereas the use of photocatalytic
materials holds the promise of treating certain air pollutants.
Long-life concrete pavements also reduce the
costs of traffic delays over their life cycle by being easily
maintained in a smooth condition using techniques
that have minimal impact on traffic operations. In combination,
the properties inherent in concrete make it an
ideal, sustainable choice for constructing pavements in
an urban environment.
5. References
Adrian, W., and Jabanputra, R. 2005. Influence of Pavement
Reflectance on Lighting for Parking Lots. SN2458,
Skokie, IL: Portland Cement Association.
Akbari, H., L. Rose, and H. Taha. 1999. Characterizing
the Fabric of the Urban Environment: A Case Study
of Sacramento, California. LBNL-44688. Berkeley, CA:
Lawrence Berkeley National Laboratory, U.S. Department
of Energy.
American Concrete Institute (ACI). 2009. “Sustainability
Leads to Durability in the New I-35W Bridge.”
Concrete International. 31:2. Farmington Hills, MI: ACI.
Chicago Department of Transportation (CDOT). 2010.
The Chicago Green Alley Handbook. Chicago, IL: CDOT.
Cleveland, C. (Topic Editor). 2010. “Heat island.” In:
Encyclopedia of Earth. Cutler J. Cleveland, Ed. Washington,
D.C.: Environmental Information Coalition,
National Council for Science and the Environment.
[First published in the Encyclopedia of Earth June 29,
2010; last revised June 29, 2010.] (www.eoearth.org/
article/Heat_island; accessed August 24, 2011)
Chusid, M. 2005. “Photocatalysts, Self-Cleaning Concrete:
Photocatalysts Can Keep Concrete Clean and
Reduce Air Pollution.” Concrete Decor. 5:4:24. (www.
concretedecor.net/All_Access/504/CD504_New_Tech.
cfm; accessed August 24, 2011)
U.S. Environmental Protection Agency (EPA). 2011.
Pervious Concrete Pavements, Washington, D.C.: EPA.
(http://cfpub.epa.gov/npdes/storm water/menuofbmps/
index.cfm?action=browse&Rbutton=detail&bmp=137
&minmeasure=5; accessed August 2011)
Gadja, J.W., and M.G. Van Geem. 2001. A Comparison
of Six Environmental Impacts of Portland Cement Concrete
and Asphalt Cement Concrete Pavement. PCA R&D
Serial No. 2068. Skokie, IL: Portland Cement Association.
(www.cement.org/bookstore/profile.asp?id=9889;
accessed August 24, 2011.
Gates, A. 2011. “MoDOT Keeps Construction Project
Environmentally-Friendly.” MoDOT St. Louis District
Press Release Page. April 22. (www.modot.mo.gov/
stlouis/news_and_information/District6News.shtml?ac
tion=displaySSI&newsId=80061; accessed August 24,
2011)
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Hogan, M.C., et al. 2010. “Noise pollution”. In Encyclopedia
of Earth. Cutler J. Cleveland, Ed. Sidney
Draggan, Topic Ed. Washington, D.C.: Environmental
Information Coalition, National Council for
Science and the Environment. [First published in
the Encyclopedia of Earth July 25, 2010; last revised
December 8, 2010.] (www.eoearth.org/article/Noise_
pollution?topic=49511>; accessed August 17, 2011)
Italcementi. 2005. TX Millennium: Photocatalitic Binders.
Technical Report. Italcementi Group.
Lauber, J., M.E. Morris, P. Ulloa, and F Hasselriis. 2006.
“Comparative Impacts of Local Waste to Energy vs.
Long Distance Disposal of Municipal Waste.” Presented
at Air & Waste Management Association Conference,
New Orleans, LA. (www.energyanswers.com/pdf/
awma_final.pdf; accessed Dec. 5, 2011)
Loehr, S. (Lead Author);Cutler Cleveland (Topic Editor).
2009. “Smart Growth.” In: Encyclopedia of Earth.
Cutler J. Cleveland, Ed. (Washington, D.C.: Environmental
Information Coalition, National Council for
Science and the Environment). [First published in the
Encyclopedia of Earth December 7, 2009; Last revised
December 7, 2009] (www.eoearth.org/article/Smart_
Growth?topic=49511>; accessed August 17, 2011)
Mackun, P. and S. Wilson. 2011. “Population Distribution
and Change: 2000 to 2010.” 2010 Census Briefs.
C2010BR-01. Washington, D.C.: U.S. Department of
Commerce: U.S. Census Bureau.
National Ready Mix Concrete Association (NRMCA).
2009. Pervious Concrete Pavement: An Overview.
NRMCA. (www.perviouspavement.org; accessed
August 24, 2011)
Passchier-Vermeer, W., and W.F. Passchier. 2000. “Noise
exposure and public health.” Environ. Health Perspect.
vol. 108, Suppl 1.
Portland Cement Association (PCA). 2011. Pervious
Concrete. Skokie, IL: PCA. (www.concretethinker.com;
accessed August 2, 2011)
Rasmussen, R.O., R. Bernhard, U. Sandberg, and E.
Mu. 2007. The Little Book of Quieter Pavements. FHWA­
IF-08-004. Washington, DC: FHWA.
Rasmussen, R.O., S.I. Garber, G.J. Fick, T.R. Ferragut,
and P.D. Wiegand. 2008. How to Reduce Tire-Pavement
Noise: Interim Best Practices for Constructing and Texturing
Concrete Pavement Surfaces. TPF-5(139). Ames, IA:
National Concrete Pavement Technology Center, Iowa
State University.
Rasmussen, R.O., R. Sohaney, and P. Wiegand. 2011.
Concrete Pavement Specifications for Reducing Tire-Pavement
Noise. Tech Brief. Ames, IA: National Concrete
Pavement Technology Center, Iowa State University.
(www.cptechcenter.org/publications/surface_char_
specs_tech_brief.pdf; accessed August 24, 2011)
Rose, L., H. Akbari, and H. Taha. 2003. Characterizing
the Fabric of Urban Environment: A Case Study of Metropolitan
Houston, Texas. LBNL-51448. Lawrence Berkeley
National Laboratory.
Schaffer, D. 2009. “Concrete That Cleans Itself and the
Environment.” Presentation at Construct 2009, Indiana
Convention Center, Indianapolis, IN. (www.constructshow.com/Assets/Content/doc/FR07%20-%20ConcreteThat%20Cleans%20Itself.pdf;
accessed August 24,
2011)
Tennis, Paul D., Michael L. Leming, and David J.
Akers. 2004. Pervious Concrete Pavements. EB302.
Skokie, IL: Portland Cement Association.
TX Active®. 2011. Project Profiles. TX Active® Photocatalytic
Cements. (http://txactive.us/project.html;
accessed August 24, 2011)
U.S. Environmental Protection Agency (EPA). 2009.
Reducing Urban Heat Islands: Compendium of Strategies–Cool
Pavements. Draft. Washington, DC: U.S.
EPA. (www.epa.gov/heatisland/resources/pdf/CoolPavesCompendium.pdf;
accessed August 2011)
Van Dam, T., and P. Taylor. 2009. Building Sustainable
Pavements With Concrete. Ames, IA: National Concrete
Pavement Technology Center, Iowa State University.
(www.cproadmap.org/publications/sustainability_briefing.pdf;
accessed Dec. 5, 2011)
Wathne, L.. 2010. “Sustainability Opportunities With
Pavements: Are We Focusing on the Right Stuff?” 11 th
International Symposium on Concrete Roads. Seville,
Spain.
Marceau, Medgar L., and Martha G. VanGeem. 2007.
Solar Reflectance of Concretes for LEED Sustainable Site
Credit: Heat Island Effect. SN2982. Skokie, IL: PCA.
84 Ch. 9. CONCRETE PAVEMENTS IN THE URBAN ENVIRONMENT Sustainable Concrete Pavements A Manual of Practice

Chapter 10
ASSESSMENT OF PAVEMENT
SUSTAINABILITY
Martha VanGeem
Emily Lorenz
Tom Van Dam
It is well known that if progress toward a goal is not
measured, the goal is not likely to be met. It is essential
that the sustainable features of pavements be
assessed and quantified to recognize improvements
and guide innovation.
Previous chapters outlined the details about what
sustainability is and how concrete pavements can
be designed and constructed more sustainably. This
chapter explains how the sustainability of concrete
pavement can be assessed and what tools are available
to assist during the assessment process. It reviews
current approaches to assessing pavement sustainability,
including the emerging rating systems. It presents
the life-cycle assessment (LCA) approach as the path
to more fully quantify the environmental and social
factors contributing to the sustainability of pavements,
and discusses other, emerging approaches as well.
These tools should be used primarily to help guide
users; they should not be used for material selection.
This is an area of fast-paced innovation, with new
and updated tools constantly emerging. Some of the
tools reviewed are still undergoing development and
are thus likely to change in the coming year. As such,
readers are encouraged to obtain the most recent information
regarding the tools discussed before employing
them.

1. Why Assessments are
Important
Many product and service manufacturers make claims
about the sustainability or “greenness” of their products
and processes. It can be difficult for an owner,
agency, consultant, contractor, or specifier to sort
through these claims without an accurate, repeatable,
and objective system to assist them in their selection.
As with any engineering challenge, such as balancing
the three tenets of sustainability, tools are available
to assist. In order to make the most-informed
design decisions with regard to sustainability, one must
employ a tool or tools that allow comparison of different
design choices. The tools presented in this chapter
vary in terms of complexity and level of detail, and it is
important to understand the strengths and weaknesses
of each in order to make the best design decision for
a given project. The intent of presenting the different
environmental-impact tools is to advance the state of
the practice.
2. Economic and Environmental
Analyses
No one tool is currently available that simultaneously
considers economic, environmental, and equity (societal)
impacts. Economic impacts are often assessed
separately through life-cycle cost analysis (LCCA).
Environmental impacts can be examined through a
life-cycle assessment (LCA).
Economic Analysis
An LCCA is a powerful economic decision support
tool used in the pavement type and material selection
process. In an LCCA, the expenditures incurred over
the lifetime of a particular pavement are accounted for.
Costs at any given time are discounted to a fixed date,
based on assumed rates of inflation and the time-value
of money, using a discount rate. The most common
discount rate used in recent years is 4 percent, but
persuasive arguments are being made that this rate
should be lower, based on the fact that transportation
agencies do not have the option of investing money
that is not spent and that the level of future funding is
uncertain. Regardless of the discount rate that is used,
a sensitivity analysis should be conducted using a
range of discount rates to determine how sensitive the
outcome is to the choice of this value.
An LCCA is performed in units of dollars and is equal
to the construction cost plus the present value of
future maintenance, repair, rehabilitation, and replacement
costs over the life of the pavement. Using this
widely accepted method, it is possible to compare the
economics of different pavement alternatives that may
have different cash flow factors but that provide a similar
level of service.
Quite often, pavement designs with the lowest first
costs for new construction will require higher costs
during the pavement’s life. So, even with their lesser
first cost, these pavements will possibly have a greater
life-cycle cost. Conversely, pavements built to last
using enhanced structure and very durable materials
often have a greater first cost but a lower life-cycle
cost. Transportation agencies are familiar with the
benefits of a lower life-cycle cost, and each state highway
agency is required to do some type of LCCA when
using federal funds to support large rehabilitation or
reconstruction projects. Volatility in the cost of oil will
affect the competitiveness of concrete on a first-cost
basis (MIT 2011).
The life-cycle cost software available from the FHWA
(RealCost 2011) provides economic analysis of
agency and user costs during a pavement’s service life.
Examples of agency costs include initial engineering,
contract administration, and construction costs;
maintenance, repair, rehabilitation, and administrative
costs; and end-of-life costs such as salvage, residual, or
remaining-service-life value. User costs include vehicle
operation (normal versus work-zone) costs, delay
costs, and crash costs (FHWA 1998).
An LCCA is relevant only if equivalent pavement
structures are being compared (for example, the same
service life and design load). National standards are
available for pavements to ensure design equivalency.
In addition, the design life of the pavement alternatives
should be stated and applied consistently during
an LCCA. Analysis periods typically range around 40
years.
There is a relationship between LCCA and environmental
impacts in that some environmental benefits
86 Ch. 10. ASSESSMENT OF PAVEMENT SUSTAINABILITY Sustainable Concrete Pavements A Manual of Practice

can be converted to a monetary value. For example,
lower energy use can result in lesser operating costs.
Environmental Assessment
One of the best ways to assess the environmental (and
to some extent the societal) impacts of a product or
process is to use life-cycle assessment (LCA). Unlike
LCCA, LCA does not account for environmental
impact in monetary units but instead in terms of mass
or energy flows in and out of a set boundary. Whereas
LCCA accrues financial impacts in terms of dollars,
LCA determines environmental impacts in terms of
energy or mass use (including waste and emissions
generated).
An LCA is an environmental assessment of a product
over its life cycle. An LCA examines all aspects of a
product’s life cycle—from the first stages of acquiring
(whether harvested or extracted) raw materials
from nature to transporting and ultimately processing
these raw materials into a product (such as a pavement),
using the product, and ultimately recycling it or
disposing of it back into nature. Conducting an LCA
of a concrete pavement is necessary to evaluate the
environmental impact of the pavement over its entire
life. As will be discussed, “green” rating systems and
programs that focus only on a single criterion—such as
recycled content or CO 2 —or phase of the pavement’s
life—such as construction—provide only a partial
snapshot of the pavement’s environmental impact.
By definition, an LCA of a pavement includes environmental
effects due to the following factors:
• Extraction of materials and fuel used for energy
• Manufacture of components
• Transportation of materials and components
• Assembly and construction
• Operation, including maintenance, repair, and
user impacts such as energy for lighting and traffic
emissions
• Demolition, disposal, recycling, and reuse of the
pavement at the end of its functional or useful life
A full set of impacts—including energy use, land use,
resource use, climate change, health effects, acidification,
toxicity, and more—should be evaluated as part
of the LCA.
An LCA involves a time-consuming manipulation of
large quantities of data. A model such as SimaPro (Pré
2011) provides data for common materials and options
for selecting LCA impacts. The Portland Cement
Association publishes reports with life-cycle data on
cement and concrete (Marceau et al. 2006, 2008).
Several organizations have proposed how an LCA
should be conducted. Organizations such as the
International Organization for Standardization (ISO),
the Society of Environmental Toxicology and Chemistry
(SETAC), and the U.S. Environmental Protection
Agency (EPA) have documented standard procedures
for conducting an LCA. These procedures are generally
consistent with each other and are all scientific,
transparent, and repeatable. As defined by ISO 14044,
the four primary steps in an LCA are (ISO 2006) the
following:
• Goal and scope definition
• Life-cycle inventory (LCI) analysis
• Life-cycle impact assessment (LCIA)
• Interpretation and conclusions
Definitions related to energy, and reporting of energy
use in LCA, are controversial and thus are typically
reported in terms of primary energy and feedstock
energy. A definition of feedstock energy is “heat of
combustion of a raw material input that is not used
as an energy source to a product system, expressed in
terms of higher heating value or lower heating value”
(ISO 2006). Primary energy is “energy embodied in
natural resources prior to undergoing any humanmade
conversions or transformations” (Kydes and
Cleveland 2007).
Goal and Scope—Setting the Boundary
The usefulness of an LCA or LCI depends on where
the boundaries of a product are drawn. A common
approach is to consider all the environmental flows
from cradle to grave. It is during this phase that cut-off
Sustainable Concrete Pavements A Manual of Practice Ch. 10. ASSESSMENT OF PAVEMENT SUSTAINABILITY 87

criteria are established for input and output to the
boundary that will be quantified in the LCI stage. LCA
standards recommend establishing cut-off criteria for
mass, energy, and environmental significance. If the
results of any two LCA analyses are to be compared, it
is critical that the boundaries are the same.
During the goal and scope phase, the impact categories
to be assessed are determined, as are the types and
sources of data that will be collected. LCA standards
also outline data quality requirements, and how to
determine whether an independent, third-party review
is required.
Life-Cycle Inventory (LCI)
An LCI is the second stage of an LCA. An LCI accounts
for and quantifies all the individual environmental
flows to and from a product throughout its life cycle.
It consists of the materials and energy needed to make
and use a product and the emissions to air, land, and
water associated with making and using that product
as illustrated in Figure 10.1.
An upstream profile can be thought of as a separate
LCI that is itself an ingredient to a product. For
example, the upstream profile of cement is essentially
an LCI of cement, which can be imported into an
LCI of concrete. To get the most useful information
out of an LCI, a material should be considered in the
context of its end use. The LCI of concrete itself can
then be imported into an LCI of a product, such as a
pavement.
The LCI of materials generally does not consider
embodied energy and emissions associated with
construction of manufacturing plant equipment and
buildings, nor the heating and cooling of such buildings.
This is generally acceptable if their materials,
embodied energy, and associated emissions account for
less than 1 to 5 percent of those in the process being
studied. For example, LCA guidelines indicate that
inputs to a process do not need to be included in an
LCI if they are a small percentage of the total mass of
the processed materials or product (typically less than
1 to 5 percent); they do not contribute significantly
to a toxic emission; and they do not have a significant
associated energy consumption. An LCI does not
include labor.
Life-Cycle Impact Analysis (LCIA)
Mass and energy flowing through the system boundary
are assigned to different impact categories during
the LCIA phase. Impact categories can be classified as
endpoints or midpoints. There is debate over where
some impact categories fall. LCA practitioners generally
agree on the correlation of LCI data and midpoint
impact categories; endpoint categories typically require
that more assumptions be made between data collected
during the LCI phase and the final damage to
the ecosystem.
SETAC published a document in 1999 that attempted
to clarify impact categories and impact indicators. It
listed midpoints such as climate change, ecotoxicity,
eutrophication, and land use. Some of the endpoints
listed were loss of resources, damage to humans, and
damage to wildlife and plants.
Though endpoints may be less accurate, some are still
important to monitor during an LCA. According to
ASHRAE 189.1, results of an LCA should include the
following impact indicators (ASHRAE 2009):
Materials
Energy
Air
Land
Water
CO2
N2O
CH4
NOx
SO2
CO
VOC
Extracting
Processing
Transporting
Disposal
Operation and Maintenance
Assembly
Figure 10.1 An LCI accounts for all materials and energy needed to make and use a product, and the
emissions to air, land, and water associated with making and using that product
88 Ch. 10. ASSESSMENT OF PAVEMENT SUSTAINABILITY Sustainable Concrete Pavements A Manual of Practice

• Acidification
• Climate change
• Ecotoxicity
• Eutrophication
• Human-health effects
• Land use (or habitat alteration)
• Ozone layer depletion
• Resource use
• Smog
Weighting can be conducted during this stage of an
LCA, but it is generally preferred to list results by
impact category. According to ISO 14044, weighting
“shall not be used in LCA studies intended to be used
in comparative assertions intended to be disclosed to
the public” (ISO 2006).
Interpretation
Conclusions of the LCA are presented and analyzed
during the interpretation and conclusion phase. During
this portion of the LCA, the practitioner identifies
any significant issues from the LCI and LCIA phase.
Finally, completeness, sensitivity, and consistency checks
are performed to evaluate the quality of the analysis.
LCA Case Study
Although more owners and product manufacturers
are undertaking LCA to make design decisions, few
reports are available to the public. Reasons for this lack
of available data include concerns about disclosure of
proprietary information and unfavorable interpretation
of results by competitors and decision makers. In the
following case study, a full range of impact categories
is evaluated. Other studies, such as that conducted
by the Athena Sustainable Materials Institute (Athena
2006), considered only two impact categories.
It is strongly recommended that LCA practitioners
evaluate, at a minimum, a range of endpoint impact
categories including acidification, climate change, ecotoxicity,
eutrophication, human-health effects, land use
(or habitat alteration), ozone layer depletion, resource
use, and smog creation. It is noted that the accuracy
of some of the models used to predict the endpoint
impact categories listed previously are often not as
accurate as those used to predict the midpoint indicators
such as energy use or CO 2 equivalents. Performing
an LCA without considering these endpoint impact
indicators does not assess the full environmental
impact of a product, design, or system. Nonetheless,
the following case study illustrates how a limited LCA
evaluation can be used to significantly reduce the environmental
impacts of a given pavement type through
improved design and materials choices.
The Kansas Two-Lift Concrete Pavement Demonstration
Project was constructed on I-70 near Salina, Kansas,
in 2008 (National Concrete Pavement Technology
Center 2008). The Right Environment of Austin,
Texas, conducted an LCA to compare a traditionally
constructed pavement section (Alternative No. 1) to
the as-built two-lift pavement (Alternative No. 2). A
third alternative, an optimized two-lift design using
higher levels of recycled and industrial byproduct
material (RIBM), was also considered in the LCA. The
basic sections evaluated are illustrated in Figure 10.2,
and the mixture designs are presented in Table 10.1.
It is clear that Alternative No. 2, which is the as-built
two-lift pavement section, had a number of innovative
features beyond the use of the two-lift design. The
40-mm top-lift surface concrete used a wear-resistant
imported rhyolite coarse aggregate, but the bottom
lift concrete used locally available, non-wear-resistant
carbonate coarse aggregate. To obtain similar wear
resistance in Alternative No. 1, the conventional design
would have to use imported rhyolite coarse aggregate
for all of the concrete in the pavement, adding cost
and environmental burden.
In addition, Alternative No. 2 used a high-volume fly
ash mixture for the cement-treated base (CTB), reducing
the portland cement content significantly from
what would be present in a conventional CTB as is
used in Alternative No. 1.
Alternative No. 3 presents some additional changes
that could have been used to improve the environmental
footprint of Alternative No. 2 with no expected
negative impact on pavement performance. Although
the surface lift in Alternatives No. 2 and No. 3 were
the same, the bottom lift in Alternative No. 3 was
Sustainable Concrete Pavements A Manual of Practice Ch. 10. ASSESSMENT OF PAVEMENT SUSTAINABILITY 89

further optimized from an environmental perspective,
replacing the locally extracted carbonate coarse aggregate
with a recycled concrete aggregate obtained on
site (note this requires that sufficient recycled concrete
be available; transporting recycled concrete aggregates
long distances actually would have negative environmental
impact due to the required transportation).
In addition, the amount of portland cement in the
bottom lift was reduced from 548 lb/yd 3 to 376 lb/yd 3 ,
and 94 lb/yd 3 of fly ash was used, resulting in an overall
reduction in the cementitious content in Alternative
No. 3 compared to Alternative No. 2.
In all cases, pavement performance over the life cycle
was assumed to be identical for the three alternatives.
The LCA results for the three alternatives are presented
in Figure 10.3. As is common with the presentation of
the LCA results, they are normalized for each endpoint
impact category with the worse performing alternative
being set at 100 percent and the remaining alternatives
presented as a percent reduction. For example, considering
the global warming potential (GWP) of each
alternative, Alternative No. 1 is the worst, Alternative
No. 2 reduces the impact in this category to approximately
87 percent of Alternative No. 1, and Alternative
No. 3 has a GWP impact that is approximately 65
percent of Alternative No. 1.
Figure 10.2 Three alternatives used in a limited LCA
to determine environmental impact of design and
material choices
In all categories (other than non-hazardous waste),
Alternative No. 1 is the poorest choice from an environmental
perspective. Alternative No. 2 shows
significant improvement (greater than 10 percent), and
Alternative No. 3 shows even further improvement. It
can be seen how such an analysis can be used in combination
with design and materials choices to optimize
a concrete pavement system, significantly lowering its
environmental impact while ensuring equal or better
long-term performance.
Table 10.1 Relevant Mixture Design Features in the Kansas Two-lift LCA Evaluation
Layer Alternative No. 1 Alternative No. 2 Alternative No. 3
PCC Top Lift
PCC Bottom Lift
Cement-Treated
Base
This alternative had only a
single PCC lift composed
of the following:
• 548 lb/yd 3 cement
• Imported rhyolite
coarse aggregate
• 172 lb/yd 3 cement
• Local carbonate coarse
aggregate
• 438 lb/yd 3 cement
• 110 lb/yd 3 fly ash
• Imported rhyolite coarse
aggregate
• 548 lb/yd 3 cement
• Local carbonate coarse
aggregate
• 78 lb/yd 3 cement
• 94 lb/yd 3 fly ash
• Recycled concrete coarse
aggregate
• 438 lb/yd 3 cement
• 110 lb/yd 3 fly ash
• Imported rhyolite coarse aggregate
• 376 lb/yd 3 cement
• 94 lb/yd 3 fly ash
• Recycled concrete coarse aggregate
• 78 lb/yd 3 cement
• 94 lb/yd 3 fly ash
• Recycled concrete coarse aggregate
90 Ch. 10. ASSESSMENT OF PAVEMENT SUSTAINABILITY Sustainable Concrete Pavements A Manual of Practice

Work continues to develop user-friendly LCA tools for
use in considering the entire pavement life cycle. Once
such tools are available, transportation agencies will
have a mechanism to more fully consider the life-cycle
impacts of design and materials choices.
3. Rating Systems
Currently, in an attempt to consider sustainable pavement
practices, a number of rating systems are emerging.
Rating systems will often use elements of the
LCCA and LCA, integrated with other environmental
and equity impacts, to assign points to alternatives
in an attempt to assess overall sustainability. Two of
the most widely known rating systems, GreenLITES
and Greenroads, are reviewed below, but there are
a number of similar systems in existence and new
systems continue to emerge, including the FHWA’s
INVEST Sustainable Highways Self-Evaluation Tool
(www.sustainablehighways.org/) and the Institute of
Sustainable Infrastructure’s envision TM rating system
(www.sustainableinfrastructure.org/). Both of these are
based on the Greenroads system.
GreenLITES
GreenLITES (Leadership in Transportation and Environmental
Sustainability) was developed by the New
York State Department of Transportation (NYSDOT)
for the certification of project designs before they go
to bid. The objectives of GreenLITES are the following
(NYSDOT 2010):
• Recognize and increase “the awareness of the
sustainable methods and practices already incorporated
into the project design”
• Expand “the use of these and other innovative alternatives
which will contribute to improving transportation
sustainability”
A self-certification program, GreenLITES allows the
project team to evaluate a project’s sustainability before
releasing it for bid. Based on evaluation of 26 recently
completed designs, certification levels are scored and
are given in Table 10.2.
Table 10.2 GreenLITES Certification Levels
Certification Level Point Range Percentile Range
Non-certified 0 – 14 < 33%
Certified 15 – 29 33 - 67%
Silver 30 – 44 67 - 90%
Gold 45 – 59 90 - 98%
Evergreen 60 and greater 98 and greater
Figure 10.3 Results of the LCA of the three Kansas two-lift alternatives (from the Right Environment,Austin,Texas)
Sustainable Concrete Pavements A Manual of Practice Ch. 10. ASSESSMENT OF PAVEMENT SUSTAINABILITY 91

The project design elements are compared to the
objectives and credit descriptions for each of the following
five GreenLITES categories:
• Sustainable sites
• Water quality
• Materials and resources
• Energy and atmosphere
• Innovation/unlisted
using local materials to the “greatest extent possible to
minimize haul distances.” The following subcategories
are included:
• Reuse of materials
• Recycled content
• Locally provided material
• Bioengineering techniques
• Hazardous material minimization
Sustainable Sites
This category focuses on the location of the project
and includes measures that can “protect and enhance
the landscape’s ability to regulate climate, provide
cleaner air and water, and improve quality of life.” This
follows NYSDOT’s policy to select the “best available
alternative based on program / project goals and objectives,
public involvement, and overall sustainability.”
The following subcategories are included:
• Alignment selection
• Context-sensitive solutions
• Land use/community planning
• Protect, enhance, or restore wildlife habitat
• Protect, plant, or mitigate for removal of trees and
plant communities
Water Quality
This category seeks to protect bodies of water by
“improving water quality and reducing storm water
runoff.” The design will be evaluated through the following
subcategories:
• Storm water management including volume and
quality
• Reduced run-off and associated pollutants by treating
storm water runoff through best management
practices (BMPs)
Materials and Resources
This category encourages the reduction of waste by
reusing and recycling materials in beneficial ways and
Energy and Atmosphere
This category’s goal is to minimize climate change
impacts through energy conservation and efficiency. It
supports air-quality improvement projects and encourages
car pooling, mass transit, and non-motorized
transportation. The subcategories included are the
following:
• Improved traffic flow
• Reduced electrical consumption
• Reduced petroleum consumption
• Improved bicycle and pedestrian facilities
• Noise abatement
• Stray light reduction
Innovation/Unlisted
This category gives credit to designs that further
GreenLITES strategies or to significant innovations
in the project related to sustainability. Each agency is
responsible for identifying what is important to them
and will likely have different criteria.
Limitations
Many of the point categories lack specific amounts or
levels of improvement required to receive the designated
number of points; the points are followed by a
list of items, and it is not clear how many of them are
required to obtain the points. It is also unclear if the
NYSDOT has specific improvement percentages or
material use rates on which they will base the point
rewards.
92 Ch. 10. ASSESSMENT OF PAVEMENT SUSTAINABILITY Sustainable Concrete Pavements A Manual of Practice

Specific examples of potential limitations related to use
with concrete pavements include the following:
• Re-use of materials (M-1 general) – This does not
include concrete mix designs which optimize alternative
materials (such as fly ash, silica fume, etc.) to
meet the pavement or structure requirements.
• Reduce electrical consumption (E-2) – This rewards
projects that utilize low energy-consuming lighting
equipment but doesn’t mention the use of concrete
pavements which may require less total lighting due
to its reflectivity. Also, although the section is titled
“Reduce Electrical Consumption,” it does not consider
electrical consumption during the extraction,
manufacture, or construction phases for materials.
• Reduce petroleum consumption (E-3) – This includes
project aspects that reduce petroleum consumption
of the project including park-and-ride areas, public
transportation connections, and design attributes
that will limit maintenance fuel use. This item does
not mention the reduction of vehicle fuel use by
riding on concrete pavements. Also, although the
section is titled “Reduce Petroleum Consumption,”
it does not consider petroleum consumption during
the extraction, manufacture, or construction phases
for materials.
Greenroads
Greenroads attempts to measure performance of
sustainable roadway design and construction. The
performance metric was developed by a team headed
by the University of Washington (UW) and CH2M
HILL (Muench et al. 2011). The Greenroads program
attempts to quantify the sustainable attributes of
a roadway project and is a tool for the following:
• Defining project attributes that contribute to roadway
sustainability
• Accounting for sustainability-related activities
• Communicating sustainable project attributes
• Managing and improving roadway sustainability
• Certifying projects
The Greenroads program has two major bestpractice
categories, mandatory and voluntary.
Greenroads applies only to roadway design and
construction. The mandatory best practices—Project
Requirements—provide the minimum level of sustainable
activities and each must be met as part of this
metric. The voluntary practices—Voluntary Credits—
are the optional attributes which show how the project
has moved toward a truly sustainable endeavor.
For a roadway project to be evaluated, the project team
overseeing the work will document how the Project
Requirements have been met and which Voluntary
Credits are being pursued. The Greenroads team
verifies the application and the point totals and assigns
the certification level. The levels include those shown
in Table 10.3.
Project Requirements
The Project Requirements are as follow:
• Environmental review process, which requires the
project team to perform an environmental review of
the project
• Life-cycle cost analysis performed according to the
Federal Highway Administration’s Life-Cycle Cost
Analysis in Pavement Design (FHWA 1998)
• Life-cycle inventory of final pavement design
(reporting global warming potential and total
energy only) using PaLATE v2.0 (Consortium
on Green Design and Manufacturing 2011) or
approved equal
• Quality control (QC) plan that lists responsibilities
and qualifications of QC personnel and QC procedures
during construction
• Noise mitigation plan needs to be established and
implemented during construction
Table 10.3 Greenroads Certification Levels
Certification Project Voluntary
Level Requirements Credits
Certified All 32 – 42
Silver All 43 – 53
Gold All 54 – 63
Evergreen All 64 and greater
Sustainable Concrete Pavements A Manual of Practice
Ch. 10. ASSESSMENT OF PAVEMENT SUSTAINABILITY 93

• Waste management plan needs to be established
and implemented during construction
• Pollution prevention plan for storm water that
meets EPA Construction General Permit or local
requirements, whichever is more stringent
• Low-impact development hydrologic analysis must
be considered for storm water management in the
right-of-way
• Pavement management system to maintain and
operate a pavement including evaluation and documentation
of preservation actions
• Site maintenance plan for roadway maintenance,
storm water system, vegetation, snow and ice, traffic
control infrastructure, and cleaning
• Educational outreach to the community as part of
the operation of the roadway
Voluntary Credits
The optional Voluntary Credits are the attributes
which show how the project has moved beyond the
minimum requirements. There are 37 voluntary practices
which are scored from one to five points each
for a total of 108 points. Custom credits are available
per the approval of the Greenroads program for up
to an additional ten points. The voluntary credits are
grouped into the following categories:
• Environment and water
• Access and equity
• Construction activities
• Materials and resources
• Pavement technologies
• Custom credit
The environment and water subcategories are as follow:
• Environmental management system
• Runoff flow control
• Runoff quality control
• Storm water cost analysis
• Site vegetation
• Habitat restoration
• Ecological connectivity
• Light pollution
The access and equity subcategories are as follow:
• Safety audit
• Intelligent transportation systems
• Context-sensitive solutions
• Traffic emissions reduction
• Pedestrian access
• Bicycle access
• Transit access and high-occupancy vehicle (HOV)
access
• Scenic views
• Cultural outreach
The construction activities subcategories are:
• Quality management system
• Environmental training
• Site recycling plan
• Fossil fuel reduction
• Equipment emissions reduction
• Paving emissions reduction
• Water use tracking
• Contractor warranty
The materials and resources subcategories are the
following:
• Life-cycle assessment
• Pavement reuse
• Earthwork balance
• Recycled materials
• Regional materials
• Energy efficiency
94 Ch. 10. ASSESSMENT OF PAVEMENT SUSTAINABILITY Sustainable Concrete Pavements A Manual of Practice

The pavement technologies subcategories are the
following:
• Long-life pavement
• Permeable pavement
• Warm-mix asphalt
• Cool pavement
• Quiet pavement
• Pavement performance tracking
Greenroads custom credit subcategory “Recognize[s]
innovative sustainable roadway design and construction
practices.”
Limitations
The Greenroads program recognizes some limitations
in the system such as improvements in the
upstream supply chain that may not be captured. For
example, the production and manufacture of materials
are not explicitly considered outside of the life-cycle
inventories and assessments.
The Greenroads program also does not explicitly
include additional roadway structures such as bridges,
tunnels, walls, or other structures in the analysis. The
program also does not explicitly include non-roadway
structures such as luminaires, barriers, and walls. Nor
does the program evaluate long-term maintenance
beyond what is “planned” in various requirements and
voluntary credits.
The long-life pavement credit does not accurately
represent long life for either concrete or asphalt pavements,
focusing exclusively on pavement thickness
and ignoring the multitude of other design and construction
details that truly produce pavements of long
life. Further, it ignores regional and climatic differences
which play a strong role in determining what contributes
to long pavement life. Of particular concern
from the perspective of the concrete paving industry
is that according to the long-life pavement credit, for
a lifetime equivalent single-axle load (ESAL) less than
500,000, the Greenroads program says that a 7-in.
thick concrete pavement is equivalent to a 6-in. thick
hot-mix asphalt (HMA) pavement. Over 50,000,000
ESALs, pavements qualify for the long-life pavement
credit with 13 in. of concrete or 14 in. of HMA. The
validity of this approach is highly questionable.
Specific examples of potential limitations related to use
with concrete pavements include the following:
• Life-cycle inventory (PR-3) – The project team is
required to complete the PaLATE Version 2.0
software tool for the project and report the total
energy use and global warming potential in CO 2
equivalents. Other life-cycle software tools may be
used if they output the total energy use and global
warming potential by means of a transparent interface
which clearly references data sources. Overall,
more impacts than just energy and CO 2 should be
reported in a life-cycle inventory.
• Light pollution (EW-8) – This category rewards
projects that use lamps that prevent light pollution
but doesn’t mention the use of concrete pavements,
which may require less total lighting due to its
reflectivity.
• Paving emissions reduction (CA-6) – Although this
category is a benefit to worker safety and the environment
around HMA paving operations, it may
be appropriate for concrete paving operations to
receive points because they do not have these air
emissions that need to be controlled. Greenroads
should be encouraged to allow an alternative for
which concrete pavements can earn credit.
• Energy efficiency (MR-6) – This category rewards
projects that use low energy consuming equipment
but doesn’t mention the use of concrete pavement,
which may require less total lighting due to its
reflectivity.
4. Summary
Assessing pavement sustainability is an essential element
in making pavements more sustainable, as it is
well known if something is not measured, it will not
get done. Although the concept of assessing sustainability
is not difficult, in practice, it is very complex.
The use of LCCA to determine life-cycle economic
costs is a mature and accepted approach to compare
alternative pavement designs. Environmental impacts
can be assessed using an LCA, but readily accessible
Sustainable Concrete Pavements A Manual of Practice Ch. 10. ASSESSMENT OF PAVEMENT SUSTAINABILITY 95

tools are not available, and gaps in the data and
knowledge limit this approach at the current time.
Emerging pavement sustainability rating systems
provide a means to currently assess pavement sustainability,
but limitations that exist in these systems mean
that they should be used to help guide users in making
their practices more sustainable but should not be
used in absolute terms to determine which pavement
alternative is more sustainable compared to another.
These tools should be used to advance the state of the
practice, not for material approval or selection.
5. References and Resources
American Society of Heating, Refrigerating, and Air-
Conditioning Engineers (ASHRAE). 2009. Standard for
the Design of High-Performance Green Buildings. ANSI/
ASHRAE/USGBC/IES Standard 189.1-2009. Atlanta,
GA: ASHRAE.
Athena Institute. 2006. A Life Cycle Perspective on
Concrete and Asphalt Roadways: Embodied Primary
Energy and Global Warming Potential. (www.athenasmi.
org/publications/docs/Athena_Update_Report_LCA_
PCCP_vs_HMA_Final_Document_Sept_2006.pdf;
accessed Dec. 5, 2011)
Federal Highway Administration (FHWA). 1998.
Life-Cycle Cost Analysis in Pavement Design–In Search of
Better Investment Decisions. FHWA-SA-98-079. Washington,
D.C.: FHWA. (http://isddc.dot.gov/OLPFiles/
FHWA/013017.pdf; accessed Dec. 5, 2011)
International Organization for Standardization (ISO).
2006. Environmental Management—Life Cycle Assessment—Requirements
and Guidelines. ISO 14044.
Geneva, Switzerland.
Kydes, A., and C. Cleveland. 2007. “Primary energy.”
In Encyclopedia of Earth. Cutler J. Cleveland, Ed. Washington,
D.C.: Environmental Information Coalition,
National Council for Science and the Environment.
[First published in the Encyclopedia of Earth August
14, 2007; last revised August 14, 2007]. (http://www.
eoearth.org/article/Primary_energy; accessed April 15,
2011)
Marceau, M.L., M.A. Nisbet, and M.G. VanGeem.
2006. Life Cycle Inventory of Portland Cement Manufacture,
R&D Serial No. 2095b. Skokie, IL: Portland
Cement Association.
Marceau, M.L., M.A. Nisbet, and M.G. VanGeem.
2007. Life Cycle Inventory of Portland Cement Concrete.
R&D Serial No. 3011. Skokie, IL: Portland Cement
Association.
Muench, S.T., J.L. Anderson, J.P. Hatfield, J.R. Koester,
M. Söderlund, et al. 2011. Greenroads Manual
v1.5.J.L. Anderson, C.D. Weiland, and S.T. Muench,
Eds. Seattle, WA: University of Washington. (www.
greenroads.us/1/home.html; accessed Dec. 5, 2011)
New York State Department of Transportation (NYS­
DOT). 2010. GreenLITES Project Design Certification
Program.
PRé Consultants. 2011. SimaPro 6. Amersfoot, the
Netherlands.
Society of Environmental Toxicology and Chemistry
(SETAC), SETAC-Europe: Second Working Group on
LCIA (WIA-2). 1999. Best Available Practice Regarding
Impact Categories and Category Indicators in Life Cycle
Impact Assessment. Brussels, Belgium.
National Concrete Pavement Technology Center. 2008.
Various resources on Two-Lift Concrete Paving. Ames,
IA: Iowa State University (www.cptechcenter.org/projects/two-lift-paving/index.cfm;
accessed Dec. 5, 2011)
Consortium on Green Design and Manufacturing.
2011. PaLATE: Pavement Life-cycle Assessment Tool
for Environmental and Economic Effects. University of
California-Berkeley (www.ce.berkeley.edu/~horvath/
palate.html; accessed Dec. 5, 2011)
Santero, N., A. Loijos, M. Akbarian, and J. Ochsendorf.
2011. Methods, Impacts, and Opportunities in the
Concrete Pavement Life Cycle. Concrete Sustainability
Hub, Massachusetts Institute of Technology.
96 Ch. 10. ASSESSMENT OF PAVEMENT SUSTAINABILITY Sustainable Concrete Pavements A Manual of Practice

Chapter 11
CONCLUSIONS AND FUTURE
DEVELOPMENTS
Peter Taylor
Tom Van Dam
Are pavements perfectly sustainable? No. Like any
other infrastructure system, their construction and
maintenance consume nonrenewable resources, generate
waste, and consume energy. More significantly,
users of modern vehicles have a significant negative
environmental and social impact as they travel on
any pavement, with respect to such aspects as energy
consumption, emissions, and noise. Pavements also
interact directly with the environment and society,
impacting such things as local temperatures and surface
run-off.
On the other hand, modern civilization would be
inconceivable without the ability to move goods,
people, and expertise quickly and affordably over large
distances via surface transportation.
Therefore, to establish a more sustainable pavement
system, both the negative and positive economic, environmental,
and social impacts must be considered and
alternatives sought that minimize the negative while
maximizing the positive. Fundamental to advancing
sustainability is the need to identify the parameters
critical to success and understand how these parameters
may be modified in such a way that significant
and continued improvement can be achieved.
In this regard, concrete pavements have a good story
to tell, as they have been effectively used for generations
to support economic and social good over the
life cycle and provide many opportunities for further
improving their sustainability in the future.
The first 10 chapters of this publication define sustainability
concepts and how they may be considered
when designing, building, and maintaining concrete
pavements. They also identify a number of easily
implementable strategies that can be employed to
improve the sustainability of concrete pavements,
plus the parameters and tools for measuring these
improvements. This chapter briefly summarizes this
information and provides an overview of innovative
approaches.

1. Review
Sustainability-related concepts related to pavements
can be applied in practical and holistic ways in every
stage of a concrete pavement: design, materials selection,
construction, use, renewal, and end-of-life
recycling. Urban environments provide unique opportunities
for implementing concrete pavement solutions
that enhance sustainability. Determining the success
of these strategies requires a systematic approach to
selecting and measuring performance criteria.
Pavement Sustainability Concepts
To date, decision making by pavement professionals
has largely been based on consideration of the bottomline,
which was understood in purely economic terms.
To advance sustainability, the bottom line must be
expanded to include environmental and societal terms.
Sustainability is also much broader than the application
of a number of individual activities but needs to
be approached system-wide.
Essential to understanding sustainability is an understanding
of how the current consumption-based
industrial system negatively impacts social systems.
The concept of a regenerative, circular economy
should be adopted, along with greater use of renewable
resources and a reduction in accumulating waste.
Ideally, the system will ultimately mimic nature, in
which the concept of waste is eliminated and all waste
becomes raw material for another process.
Sustainability also requires the adoption of a life-cycle
perspective, in which the economic, environmental,
and social benefits and costs of any product or service
are considered over its entire life, requiring a cradleto-cradle
approach in which the end of life is part of a
new beginning.
Designing Sustainable Concrete
Pavements
Sustainability is not an accident. Design plays a very
strong role in ensuring that the constructed concrete
pavement begins its life with sustainability in mind,
which requires a thoughtful approach to the design of
the whole pavement. The designer must follow several
principles:
• Account for human needs and values while considering
the environmental setting in which the pavement
will be constructed.
• Make engineering decisions that will ensure that the
pavement will perform as desired for the intended
life (likely 40 years or more). Design features of
long-life concrete pavements include the following:
◦ Adequate thickness
◦ Strong, erosion-resistant bases
◦ Doweled transverse joints, or continuously
reinforced concrete pavement where volume of
traffic requires them
◦ Appropriate materials and proportioning for
durability, economy, and reduced environmental
impact
◦ Timely maintenance and rehabilitation
• Choose systems and approaches that will have
minimum economic, environmental, and social
cost, without compromising engineering quality.
• Design for what is needed. Overdesign is wasteful,
but under-design is even more wasteful because
longevity of the system may be compromised.
• Consider the impact of alternative approaches and
conduct sensitivity analyses.
Innovation that meets these goals should be encouraged.
Selecting Materials
The materials used in making paving concrete have
a significant impact on the sustainability of the pavement
because their production and transport to the
site have relatively large impacts and they directly
impact long-term performance.
Manufacturing portland cement is an energy intensive
process that requires crushing, grinding, and heating
raw materials and grinding the clinker at the end
of the process. It also has a high CO 2 burden, as the
decomposition of calcium carbonate (CaCO 3 ) rock
into calcium oxide (CaO) and CO 2 is an inherent part
of the process. The environmental burdens associated
with a concrete pavement can be reduced by any combination
of five actions:
98 Ch. 11. CONCLUSIONS AND FUTURE DEVELOPMENTS Sustainable Concrete Pavements A Manual of Practice

• Make the manufacturing process more efficient
• Reduce the amount of portland cement clinker in
the cement
• Reduce the amount of cement in the concrete mixture
• Use less concrete in a pavement over the life cycle
• Extend the useful life of the pavement
SCMs are common byproducts from other industries
that beneficially react with portland cement to enhance
long-term performance. Thus, the effective use of
SCMs not only reduces the amount of portland cement
required, it also reduces the need to dispose of what
otherwise would be industrial waste. This is often done
at reduced economic cost.
Aggregates comprise the bulk of the volume of a
concrete mixture and generally have the lowest environmental
impact. Creating a desired aggregate grading
and using as large a nominal maximum aggregate
size as practical for a given situation will allow the
reduction of the amount of cementitious materials
required in a mixture. In general, aggregates have
limited direct impact on the durability of a mixture
except for D-cracking and AAR, which can be avoided
through material testing and application of mitigation
strategies.
Recycled concrete and other construction waste can be
used as aggregates in paving concrete and supporting
layers, reducing the demand for virgin aggregates and
also reducing the need to place the waste materials into
landfills.
Chemical admixtures are used in small quantities;
therefore. their direct environmental impact is small.
Their overall impact, however, is large, as they can be
used to significantly reduce the amount of cementitious
material required to achieve performance, and
they can markedly improve potential durability of a
mixture.
The goal of mix proportioning is to find the combinations
of available and specified materials that
will ensure that a mixture is cost effective, meets all
required performance requirements, and does this at
the lowest environmental and social cost over the life
cycle. In the case of sustainable design, reducing the
life-cycle environmental footprint (e.g., embodied
energy and GHG emissions) must be one of the performance
requirements considered.
Construction
The construction phase is of relatively short duration
when compared to the total life of a concrete
pavement. However, initial construction quality has
a significant influence on the concrete pavement’s
service life, which in turn directly impacts life-cycle
economic, environmental, and social costs. What may
be intended to be a sustainable pavement through
enhanced design and optimized material selection
can turn out be be non-sustainable due to improper
construction processes and/or a lack of quality control
which leads to premature failure.
The energy consumed during construction also needs
to be considered as well as the environmental and societal
impacts incurred during the construction phase.
Construction processes and equipment should be optimized
to minimize fuel consumption and emissions.
Environmental and societal impacts associated with
the construction phase include the following:
• Erosion and storm water runoff
• Emission of CO 2 and particulates through equipment
exhaust stacks
• Emission of airborne dust particulate from construction
processes
• Noise generated from construction processes
• Slurry run-off from wet sawing joints
• Increased road user cost due to traffic delays caused
by construction
The Use Phase
The use phase, particularly the traffic using the facility,
has the largest life-cycle impact on the environment.
These impacts include not only energy consumption
and emissions but also noise, run-off, and temperature.
Vehicle fuel consumption depends on many factors
that are the same regardless of pavement type.
However, pavement roughness, surface texture, and
Sustainable Concrete Pavements A Manual of Practice
Ch. 11. CONCLUSIONS AND FUTURE DEVELOPMENTS 99

stiffness can be controlled by the managing agency,
which has the ability to design, construct, and maintain
a pavement surface that will minimize the economic,
environmental, and social impact of vehicle
operations.
Other use phase factors that warrant consideration
include solar reflectance, lighting needs, long-term
concrete carbonation, water run-off, and traffic delays.
Pavement Renewal
Preservation and rehabilitation play an important role
in ensuring pavement longevity while maintaining an
acceptable level of serviceability. Long-lasting pavements
reduce future investment in new materials and
construction, thus minimizing economic, environmental,
and social impact over the life cycle. A well maintained
concrete pavement will remain in a smooth,
safe, and quiet condition for a greater duration of its
life, thus increasing the fuel efficiency of vehicles,
reducing crashes, and minimizing social impact due to
noise.
Renewal strategies that can be applied to concrete
pavements to maintain serviceability over the design
life include preventive maintenance and rehabilitation.
Preventive maintenance is a planned strategy
employing treatments that extend pavement life generally
without increasing structural capacity. Pavement
rehabilitation adds some structural capacity, usually
through the application of additional pavement thickness
in the form of an overlay.
Initially, pavement condition decreases slightly with
time as the pavement ages and is subjected to traffic. If
left unattended after this initial phase of the pavement
life, performance decreases at an increasing rate before
finally leveling off once it has reached a poor condition.
Preventive maintenance is applicable during the
initial phase when the pavement is in relatively good
condition and has significant remaining life. Pavement
rehabilitation is appropriate once the pavement
condition has dropped to a point where it is no longer
effective to apply preventive maintenance. Reconstruction
is ultimately the only suitable alternative once the
pavement condition has dropped below a given level.
End of Life
At the end of life, a concrete pavement should be
completely recycled. The ultimate goal of recycling is
to develop a zero waste stream utilizing all byproduct
materials in the rehabilitation or reconstruction of
a concrete pavement. Not only is this economically
advantageous, local recycling minimizes environmental
impact by reducing the carbon footprint, embodied
energy, and emissions as well as enhancing social good
by reducing the need for landfills and the extraction of
nonrenewable raw materials. The concept of recycling
must be viewed as a cradle-to-cradle undertaking.
An added benefit of recycling concrete is the potential
to reduce atmospheric CO 2 through carbon sequestration,
or carbonation. Typical environmental conditions
in a pavement subsurface base system are favorable
for accelerated carbon sequestration, thus recovering
up to 50 percent of the CO 2 released during cement
manufacturing.
Hydraulic cement concrete can easily be processed
into RCA which has added value as an aggregate
replacement in new concrete, as a dense graded base
material, as drainable base material, and as fine aggregate.
The quality of RCA concrete depends primarily
on the amount of mortar that remains attached to the
original aggregate. The mechanical properties of RCA
are a function of the quality and size of the particles.
Generally RCA can be processed to have more than
adequate values of abrasion resistance, soundness, and
bearing strength.
Urban Environment
The infrastructure needs of densely populated urban
areas are significant. The include pavements, sidewalks,
water and sewer utilities, and power transmission
lines. Such systems are extremely sensitive to
disruption, which can have large social impacts when
natural or manmade disasters occur. Pavements represent
a key element in this infrastructure. Traffic congestion
and delays, smog, safety concerns, and even
aesthetics play a greater role in urban areas because
any impact has the ability to affect a larger segment
of the community and the environment as a whole.
Thus, potential strategies that may be cost prohibitive
in a rural location may now become cost effective, and
100 Ch. 11. CONCLUSIONS AND FUTURE DEVELOPMENTS
Sustainable Concrete Pavements A Manual of Practice

strategies that would not have been considered before
may now be applicable when the societal impacts are
considered.
One such example is the heat island effect, which
occurs where there is a local area of elevated temperature
located within a region of relatively cooler
temperatures. Because of the greater density of paved
and covered surfaces in urban environments, the heat
island effect occurs most frequently in urban areas. The
effects of urban heat islands are broad, not only resulting
in increased levels of discomfort but also occasionally
having an impact on human health. One strategy
for mitigating the urban heat island effect is using
reflective paving materials, including conventional
concrete. Additives that can further increase the SRI of
concrete, such as slag cement or light-colored fly ash,
are also recommended.
There are additional benefits in using light-colored
concrete pavements. Light-colored pavements can
also improve safety by improving night visibility while
reducing artificial lighting requirements, thus saving
energy and reducing emissions. In urban environments,
photocatalytic cements and/or coatings may
be a viable option to help maintain highly reflective
surfaces.
Precipitation runs off hard, impermeable surfaces (such
as pavements) much faster than off undeveloped or
vegetated ones. The concern from the standpoint of
environmental impact is that storm water systems will
be overwhelmed when large areas of vegetation are
replaced with paved or hard surfaces, resulting not
only in flooding but also in erosion and the transport
of pollution into nearby surface waters. Typical storm
water management techniques, such as retention
ponds, are difficult to implement in urban areas due to
lack of available land. Thus, sanitary sewers often are
used to handle storm water, thus resulting in increased
needs for water treatment and/or release of untreated
water. For these reasons, innovative pavement solutions
are acutely needed in urban areas, including the
use of pervious concrete pavement surfaces.
Assessment
It is essential that the sustainable features of pavements
be assessed and quantified to recognize improvement
and guide innovation. Many product and service
manufacturers make claims about the sustainability
or “greenness” of their products and processes. It can
be difficult for an owner, agency, consultant, contractor,
or specifier to sort through these claims without
an accurate, repeatable, and objective system to assist
them in their selection. In order to make the most
informed design decisions with regard to sustainability,
decision makers must employ a tool or tools that allow
comparison of different design choices.
No one tool is currently available that simultaneously
considers economic, environmental, and societal
impacts. Economic impacts are often assessed
separately through life-cycle cost analysis (LCCA).
Environmental impacts can be examined through a
life-cycle assessment (LCA). Tools to assess societal
impacts are still in their infancy.
To address this need, a number of pavement sustainability
rating systems are emerging. Rating systems will
often use elements of the LCCA and LCA, integrated
with other environmental and societal impacts, to
assign points to alternatives in an attempt to assess
overall sustainability.
2. Innovation
Dramatic improvements in concrete pavement sustainability
will require the adoption of innovations. Some
innovative approaches have been used in demonstration
projects and show promise for implementation.
Others still require research.
Several technologies have been adopted in response to
implementing sustainability principles. These include
the following:
• Changes in cementitious materials systems and
mixture proportioning
• In-situ concrete recycling
• Recycling water at the concrete plant
• Pervious concrete
• Next generation quiet texturing
• Precast paving units
Sustainable Concrete Pavements A Manual of Practice Ch. 11. CONCLUSIONS AND FUTURE DEVELOPMENTS 101

Technologies at the demonstration stage include the
following:
• Two-lift construction
• Photocatalytic cements
• Inclusion of RAP in concrete mixtures
• Bubbling cement plant exhaust gases through pools
to grow algae from the CO 2 , which is then dried
and burned in the kiln as fuel
Further advances are just over the horizon:
• Low-carbon to carbon-sequestering cements
• Alternative sources of raw materials for portland
cement manufacture that will not involve the
decomposition of carbonate rock
• Energy efficient devices to convert CO 2 to solid
carbon fiber, including carbon nanotubes
• Processes to capture mercury in the cement manufacturing
process
• Mixtures that have self-healing capabilities
• Smart pavements that monitor their condition and
report when they are getting stressed
• Pavements that generate electricity to power adjacent
neighborhoods
• Geothermal heat under the pavement being captured
to melt snow
• Pervious shoulders with bacteria in them that will
treat water as it travels through the pavement
Specifications and contractual systems need to be
developed and implemented that will encourage
implementation of promising approaches. Coupled to
this is a great need to educate and train designers and
practitioners. There is plenty of challenging, exciting
work yet to be done.
102 Ch. 11. CONCLUSIONS AND FUTURE DEVELOPMENTS Sustainable Concrete Pavements A Manual of Practice

National Concrete Pavement Technology Center
2711 South Loop Drive, Suite 4700
Ames, IA 50010-8664
515-294-5798
www.cptechcenter.org